Trips and Darnold,
Interesting ideas on unsprung weight. I believe the unsprung weirht of the motor is the only drawback with pancars compared to TCs. One way to reduce it is to move the motor closer closer to the point where the rear pod pivots as it moves up and down.(the rear T-bar ball in most cases) Using a larger spur gear will help though theres a limit to how far you can move the motor forward. If you imagine the extreme cases where the pivoting point and motor is almost at same place the motor will hardly move relative to the chasis compared to the rear axle.