I'd PM you this question, but maybe a few others would like to know the answer...
Do you/can you make a passenger backrest that latches on to the existing Yamaha top-case mounting bracket? I'd love to be able to unlatch and remove the Yamaha top case, and quickly latch on a passenger backrest for Mrs. Maverick. That would prevent the hassle of removing the black, already-bolted-on mounting bracket from the rack and then bolting on a backrest, every time we need to go between setups.
I'm a tool engineer by trade and can design such a thing and have it fabricated, but time is hard to come by lately... and it appears you do very nice work.
1981 Yamaha XJ550 RH Seca
1970 Bridgestone 100 TMX
1946 Harley WL 45