I got the remaining glitches worked out, and the deal is that clustered forward rendering works great. It has more flexibility than deferred rendering and it performs a lot faster. This means we can use a better materials and lighting system, and at the same time have faster performance, which is great for VR especially. The video below shows a scene with 50 lights working with fast forward rendering
One of the last things I added was switching from a fixed grid size of 16x16x16 to an arbitrary layout that can be set at any time. Right now I have it set to 16x8x64, but I will have to experiment to see what the optimum dimensions are.
There are a lot of things to add (like shadows!) but I have zero concern about everything else working. The hard part is done, and I can see that this technique works great.