Eric hits on what I have considered doing for years but haven't yet done. Build a fork with adjustable rake but maintains head angle through the adjustment range. I have read, and seen photos, of others doing this. For a bike category (20" wheels) that has so little published data I think this experiment is a worthy consideration.

LB- How serious are you about your questions? I would consider making you a fork that you can experiment with. Of course we'd need to work through the dimensional needs and adjustment range as well as a few other aspects If you're interested let me know. Andy