I built mine to plans a few years back. Great flying plane with only a ST .61.
This is one of those planes you just don't realy need an engine twice as big as called for. It's not by any means a 3d or super aerobatic plane.
A .61 provides enough power to get it off the ground in a hurry, and to move it from point "A" to point "B" in no time, yet slow down to an almost stand still in a slight breeze.
Vertical is limited, but still very good.
When I build another one I'll still only stick a .61, or maybe as far as a .70 something, but most likely a .61.

As far as building the kit, it's been awhile since I built it. (started it in 1992.Didn't get to finish it untill 1996 due to military service) I built it per plans and the only thing I can remember I wish I would have changed was beefing up the vert fin and adding a bit to the rudder.