I’ve been grinding the F-111 line in the American air tree and I’ve gotten to the F-105. The previous vehicle is the B-57A at rank 5, there’s no rank 6 vehicle so it’s a massive gap to the F-105 at rank 7 - the F-105’s stat card says you get the usual 110% RP bonus if you research it with the previous vehicle (the B-57A) - the question is then, would grinding with the B-57A result in far less RP gain since it’s normally inefficient to grind using vehicles with a rank difference greater than 1?
I’ve asked around and no one seems to know, some think it wouldn’t be inefficient, others think it would. The game unfortunately has zero indication of what the result would be, and throwing silver lions out the window to test it is silly.