I never did report back on how this mod turned out. After riding here and there over the summer and tweaking the isolator compression, I got it to where it is pretty smooth.

I realize do that it will never be as good as it would be with the balancing shafts still in the motor, that was a tradeoff that I would think hard about making again.

In early October took the bike on a 300-mile day trip, motor ran great, no buzz or numb hands. Could have gone a couple hundred more.
Totally worthwhile project. I should have done it sooner.

05 speedmaster - 1100cc, 11:1 racing pistons, Carillo rods, thunderbike cams, ported and polished head, 2mm over intake and exhaust valves, Barnett kevlar clutch, scepter pipes, oversize manifolds, 45mm HSR's, TTP stage 4 firestarter