Based on Infogram1's INI dump I went ahead and adjusted the cache like so:
[RayTracing/BottomLevelCache]
Budget = 3221225472
EvictAgeLimit = 60
This should increase the cache size from 20MiB to 3GiB. It seemed like the VRAM allocation did increase but I'm not entirely sure. I'm also wondering if different RT settings result in different cache sizes...
Anyway, if additional people could test this, I would be more than thankful.