I'd say add brass wipers and flex wire to the engines lead, trailing and drive wheels to better accomodate the ground p/u needs...attach all those to the main chassis via a single or mutiple leads- the removable center p/u should be well insulated and be fine on its own.
I always wondered how well a convertible engine...2r/3r...would adapt between venues...seems my question is answered.
I just saw some fine flex wire the other day and am struggling to remember just where that was, but there's other wire options too so long as you keep it thin and very flexible to keep lead and trailing truck binding at bay because of the added wire.
