How to cure the "hop" of cars with torquey long cans, and flexible anglewinder chassis? Brace the rear axle mounts against the motor. This quick fix goes to the root of the the problem, first encountered in Ninco anglewinders, and now found in the otherwise-admirable Spirit Peugeot 406 series. Look through the rear window, and under that faux V-6 engine (now removed), the white styrene braces are clearly visible:
I used white Plastruct styrene tubing, but anything will do, even scrap sprue from old plastic model kits. The tubes are in compression and tension, with little twisting forces. A solid blob of Goop (rubbery, tough glue from the hardware store) across the top of the axle bearing holders, and on the motor, are all that is needed:
This fix reduced the rear axle hop, vibration, and even helps keep the guide in the slot under braking (the hop was that bad). Best lap time on my wood track dropped from 5.344 seconds to 4.951, a remarkable improvement for such a simple "tweak". And, the car is more predictable, and more fun to drive.