There are few pictures/ ideas here that got me thinking, so thanks (this is all really helpful).
I feel I’m on the right track mounting the load at the shock mounts then somehow tying into the grab rail—the salient move being to then locate the “platform” directly over those points (where the passenger sits). The big geometry problem back there seems to be keeping the load forward, and not creating a lever worse than it needs to be.
When I get further into the build I’ll look into how to post photos (then I can stop trying to explain this with words).
A question arose in thinking about this though—which might be getting me a little too far into the weeds (but I’d like to hear anyone’s opinion)…
I wonder how much of the passenger’s weight is offset be the operator. These seats (with pillion) seem like they can kind of behave like a seesaw board, having a pivot point. My seat has none of the bumpers, so it’s kind of floating (and I’ve taken my girlfriend for plenty of rides already with no weirdness.)
I wonder because if the operator’s weight isn’t doing the heavy lifting—and the passengers load lands below the passenger (aft of the shock mount/ before the end of the seat)—is to say that that part of the loop (alone) can carry 150plus pounds (…at speed, and over bumps too). If compressed my seat’s back end land on the grabrail mounts.
I won’t be resting my rack on the seat, but if I tie into where the passengers weight falls (and load over it—not away from it) I should, arguably, be able to carry a passenger on my rack, yes?
Or, again, the operator is holding them up, and their weight alone would collapse the bikes back end.
Either way, I should be fine, but I did have the thought.