I really don't know what Winnie's justification for not stretching your chassis more than they did could be. Stretch Plus Two Feet More in Front of the Axle and Minus Two Feet Behind... Cost would have to be just about a wash.
I've tracked Harvard's progress toward good handling from Day One and what he did with Caster was close to miraculous. Hopefully it'll help you. Still, with all that overhang and the short wheelbase ratio, I'm becoming convinced you're going to need all the help you can build into (under) that coach.