Sparky,
My Beaver was a handfull on the first taxi test. I tweeked the landing gear slightly to add toe-in. Ya gotta be concerned about spiltting the gear fairing though. I took the axles off and gave the gear a slight twist, not enough to be able to see iton th ergear legs. On my next Beaver, I'm gonna slot the inner gear screw hole slightly so I can add the toe-in.
Not sure why yours is so sensitive on aileron. Mine was just fine with the book settings and 30% expo, using a Spektum DX-7.