I tried several things with the bottom cushion. Seating the bottom cushion all the way back into the seat does not improve things -- I had already tried this. And there is no moving the back cushion as they are attached and firmly sprung. However, lining up the front of the cushion with the base that it rest on and then cramming the cushion into the back of the seat actually helps to keep enough of the cushion out of the foot rest so that it can latch properly. I say enough of the cushion , because the bottom of the cushion casing still gets pinched a bit by the footrest. Would using a different style cushion core alleviate this? Would any particular type of core be more resistant to rolling over?

As for the mechanism, I think I could probably handle installing it myself. Would there be instructions? It looks pretty straight forward, but some guidance might make the job quicker.

Finally, would it be possible to upgrade to the power unit? If the mechanism has to come out anyway, I thought I would ask. What would something like that cost?

Again, I thank you for your help here. It's things like this that make me glad I purchased from such a reputable dealer.