Hi Maxbrown,
I think thats very smart mix use of cpu and gpulightmass in your case. I havent do any VR scene yet cant response yet.
You also reminded me the Luoshuang GPU lightmass plugin, i though it was a UE4 thing didnt know they keep updating for UE5 too.
I use Luoshuang most of the time, the rendering i do using GPU lightmass is much nicer than the CPU does.
Sadly all the Luoshuang gpu dropbox link are down now, dont know why, will give it a try once I get the files.
Leo