After changing MPC-HC's internal LAV video decoder to CUVID, and changing madVR's chroma upscaling algorithm to Bilinear and image downscaling algorithm to DXVA2, I now get an SVP Index of 1 and render times < 2ms.
I do, however, get > 4000 dropped frames per minute and am not sure why. I'll make some more settings tweaks later.
Many thanks for your help, Chainik =]

For anyone reading this in the future, I used this forum post to help with madVR's stats and settings:
https://yabb.jriver.com/interact/index. … c=124136.0

Thanks for the fast reply!

I tried AVSF instead of fddshow in MPC-HC, but the SVP index is still roughly the same. ~0.77. CPU utilisation now fluctuates between ~35-45% and GPU utilisation is ~70%.

With a 3840x1920@59.94 video, using the automatic video profile, I can do frame rate conversion to "Fixed 240 fps" at the highest quality with high artifact masking. I get an SVP Index of 1, CPU utilisation of ~14% (AMD 5900X) and GPU utilisation of ~60% (NVIDIA 3080).

However, with a 5400x2700@59.94 video, using the automatic video profile, with "Fixed 90 fps" at the lowest quality with no artifact masking I only get an SVP index of ~0.73. The CPU utilisation is only ~14% and GPU utilisation is only ~45%. (RAM and SSD utilisation are also low)

I have followed various setup steps found on the wiki and forum, but am not sure how to further diagnose or fix the issue. Any help would be greatly appreciated =] If there's anything I can provide to give more information, please let me know.

Some info:
I'm using Windows 10 (build 19042.685) with MPC-HC (1.9.8) on a 2560x1440@240 monitor. I get similar results in SteamVR (latest beta) with Whirligig (latest beta) on an HP Reverb G2.
SVP version is 4.5.0.206.
NVIDIA drivers are version 461.92.
I have installed LAV Filters (0.74.1) and madVR (0.92.17).
In the SVP application settings I have enabled GPU acceleration and NVIDIA Optical Flow.
MPC-HC and Whirligig have been configured using https://www.svp-team.com/wiki/SVP:MPC-HC and https://www.svp-team.com/wiki/SVP:Whirligig
In CodecTweakTool (6.5.0) DirectShow Filter Configuration for LAV Video Decoder I have set the number of threads to 24 and specified NVIDIA CUVID as the hardware decoder to use.
In the MPC-HC Internal LAV filter settings I have set the number of threads to 24.
In the SVP control panel I have set the video frame settings to keep aspect ratio and normal size, and disabled outer lighting.

The events log contains the following:

15:28:53.272 [i]: Main: starting up SVP 4 Pro [4.5.0.206]... 
15:28:53.273 [i]: Main: args: none
15:28:53.274 [i]: Main: working dir is C:\Program Files (x86)\SVP 4\
15:28:53.274 [i]: Main: data dir set to C:\Users\<My User>\AppData\Roaming\SVP4\
15:28:53.281 [i]: Settings: loading main.cfg OK
15:28:53.287 [i]: Settings: loading ui.cfg OK
15:28:53.288 [i]: Settings: loading frc.cfg OK
15:28:53.291 [i]: Settings: loading profiles.cfg OK
15:28:53.296 [i]: Settings: loading custom.cfg OK
15:28:53.302 [i]: Settings: loading lights.cfg OK
15:28:53.302 [i]: Main: using Qt 5.15.1 (i386-little_endian-ilp32 shared (dynamic) release build; by MSVC 2019)
15:28:53.302 [i]: Main: device scale is 1.00001, user defined scale is 0
15:28:53.303 [i]: Main: system locale is [en-gb]
15:28:53.304 [i]: Main: setting language file to en.qm...
15:28:53.316 [i]: Main: collecting system information...
15:28:53.317 [i]: OS: Windows 10 [10.0.19042]
15:28:53.318 [i]: CPU: AMD Ryzen 9 5900X 12-Core [base frequency 3701 MHz, 24 threads]
15:28:53.318 [i]: Video: registry info - NVIDIA GeForce RTX 3080
15:28:53.319 [i]: Video: reading OpenCL info...
15:28:53.373 [i]: Video: 1 GPU OpenCL device(s) on NVIDIA CUDA [OpenCL 1.2 CUDA 11.2.162] (NVIDIA Corporation)
15:28:53.374 [i]: Video 1: GeForce RTX 3080 (NVIDIA Corporation, ver.461.92) [gpuID=11]: OK
15:28:53.374 [i]: Video 1: may support NV Optical Flow (Compute capability: 8.6)
15:28:53.374 [i]: Memory:  16294  MB total,  8238 MB free
15:28:53.374 [i]: System: finding network settings...
15:28:53.758 [i]: Power: AC is ON [1]
15:28:54.745 [W]: Main: module 'plugins/svpflow1.dll': NOT FOUND
15:28:54.745 [W]: Main: module 'plugins/svpflow2.dll': NOT FOUND
15:28:54.746 [i]: Main: module 'plugins64/svpflow1.dll': 4.5.0.200
15:28:54.747 [i]: Main: module 'plugins64/svpflow2.dll': 4.5.0.206
15:28:54.748 [i]: Main: module 'plugins64/svpflow1_vs.dll': 4.5.0.200
15:28:54.748 [i]: Main: module 'plugins64/svpflow2_vs.dll': 4.5.0.206
15:28:54.749 [i]: Main: VLC filter (64 bit): 1.0.0.190
15:28:54.749 [i]: Main: PYTHONPATH is C:\Program Files (x86)\SVP 4\mpv64
15:28:54.771 [i]: Screens: updating information, 2 screen(s) found
15:28:55.221 [i]: Main: preparing video profiles...
15:28:55.274 [i]: Main: preparing performance graphs...
15:28:55.338 [i]: Main: preparing ffdshow...
15:28:55.366 [i]: FFDShow: found 64-bit version 1.3.4533.0 [C:\Program Files\ffdshow\ffdshow.ax]
15:28:55.369 [i]: Main: preparing AviSynthFilter (AVSF)...
15:28:55.370 [i]: AVSF: found 64-bit version 0.9.4.0 [C:\Program Files (x86)\SVP 4\avsf\avisynth_filter_64.ax]
15:28:55.370 [i]: Main: preparing mpv...
15:28:55.371 [i]: VLC: installed Vapoursynth plugin: 1.0.0.190
15:28:55.371 [i]: Main: preparing remote control...
15:28:55.372 [i]: RemoteControl: started
15:28:55.372 [i]: Main: preparing main menu...
15:28:55.437 [i]: Main: loading extensions...
15:28:55.448 [i]: Extensions: found svpcast 1.1.0.205 ...
15:28:55.449 [i]: Settings: loading cast.cfg OK
15:28:55.457 [W]: Control: failed to register shortcut Meta+Ctrl+S
15:28:55.480 [i]: Extensions: found svpcode 1.1.0.206 ...
15:28:55.487 [i]: Settings: loading code.cfg OK
15:28:55.523 [i]: Extensions: found svptube 2.1.0.195 ...
15:28:55.542 [i]: Settings: loading tube.cfg OK
15:28:55.553 [i]: Tube: initializing youtube_dl...
15:28:55.584 [i]: Main: initialization completed in 2272 ms, but still waiting for the screens measurement...
15:28:55.663 [i]: Updates: checking now...
15:28:56.920 [i]: Tube: youtube_dl ready
15:28:57.420 [i]: Screens: screen 1 - 2560x1440 @240.806 Hz [measured], x1.0 [108 DPI]
15:28:57.488 [i]: Streaming: Bonjour service is not available, AppleTVs are probably not discoverable
15:28:57.562 [i]: Screens: screen 0 - 2560x1440 @240.860 Hz [measured], x1.0 [108 DPI]
15:28:57.562 [i]: Screens: primary screen is 0
15:28:57.670 [i]: Performance: quick estimation = 871 (previous value was 942)
20:00:14.931 [i]: VideoPlayer: new ffdshow video [70a62] in mpc-hc64.exe (64-bit) [MPC-HC 1.9.8.0] on screen 0
20:00:15.029 [i]: Media: video 5400x2700 [PAR 1.000] at 59.940 fps [variable]
20:00:15.029 [i]: Media: codec type is HEVC, YUV/4:2:0/8 bits/BT.709 BT.709
20:00:15.031 [i]: Playback: starting up...
20:00:15.034 [i]: Playback [70a62]: Frame server (64-bit) 3.5.0.0, AviSynth+ 3.5 (r3106, 3.5, x86_64), C:\WINDOWS\SYSTEM32\avisynth.dll
20:00:15.035 [i]: Playback [70a62]: resulting video frame 5400x2700
20:00:15.035 [i]: Playback [70a62]: 1 acceptible profiles, best is 'Automatic' [0]
20:00:15.036 [i]: Playback [70a62]: enabled while video is playing
20:00:15.037 [i]: Profile: using automatic profile #1 /film
20:00:15.039 [i]: Playback [70a62]: playing at 89.91 [59.94 *3/2] 
20:00:56.039 [i]: FFDShow: remove instance [70a62]
20:00:56.040 [i]: Playback [70a62]: disabled while video is stopped
20:00:56.342 [i]: Playback [70a62]: deleted

For the videos I've tried with a resolution 4K and under SVP has worked brilliantly and I've been very happy with it. Great piece of software =]

Many Thanks,
Denyer.