I was thinking of the fact that the B-29 pilots had a control wheel and used their own ailerons, and so did both F-84 pilots, with sticks.
For the sake of discussion only, suppose the B-29 pilots, flying an aircraft with a known VERY slow roll response, wanted to bank left and the F-84 pilots tried NOT to bank left. To me, it seems like each F-84's set of ailerons would cancel each other out and the B-29 should bank left. But what if only ONE F-84 pilot tried not to bank left? Then, it seem to me as if the F-84's ailerons would still cancel each other out, but the deflected ailerons would add drag to that side. It would be OK of the guy trying not to bank left was on the left side, but would cause considerable adverse yaw if he was on the right side (drag on the extreme right when the B-29 was trying to bank left.
The worst scenario I can think of would be that when they decided to release the F-84s, ONE released and the other one wouldn't.
I'm starting to get curious how that thing could taxi and took off, and am assuming that maybe they coupled together in-flight? Does that even seem possible?
Just thinking about the contraption in print ... I'll stop ...