Excellent topic to really dig into during winter months! I’ve turned this idea around in my head thousands of times over the years.
I don’t have hard data, but of course if you hop in the seat, you can see your RPM jump as you lighten the rear wheels. Newton’s Third would say that every action has an equal and opposite reaction, so if you hop and it causes the kart to bounce and lighten, it also has to land back down with equal force at some point, so you would think it would offset the gains. However, when you hop, if you gain let’s say 300RPM, does the engine then have more torque in that rev range and therefore when the force increases as you land from your hop, does it pull through that added force better and cancel out some of the drag you would experience?
My thought is yes, it would, so hopping would offer ever so slightly better pull off the bottom end, but it’s almost negligible. What comes up, must come down, but if you can get the engine to pull slightly harder on the come up, then the come down isn’t as detrimental.