Will the standard flybaby wings be big enough?
Increasing the weight while keeping the wings the same will increase stall speed and landing speed. The only trouble I’ve heard from the two guys who built tandems before was climb rate. That is effected by wing loading, but power loading has a larger effect, and with the horsepower increase, I expect it to climb well. If the landing roll is too long for my tastes, I’ll start fiddling with flaps, but with aggressive slipping I think it may well be fine the way it is.