I would agree. The mains are very soft...which was good when I was learning; a bit annoying now. Definately install a strip of 3/8" ply (or whatever you have >1/4") at the rear of the fuse where the tail mount will be... the balsa just doesn't stand up to the stress. Flaps are outlined in both the drawings and the instructions. If you decide to go with flaps (and you should because they're fun), I'd really recommend dual aileron servos as the mid section will be very crowded...not to mention the linkage nightmare. Standard servos fit perfectly between the ribs with only the face of the servo exposed.

I'd say a .46 fx is the perfect 2 stroke for the plane if you want to push the limits of the standard construction airframe and do some glider tows. You may also opt to reduce the dihedral fom 4" to maybe 2", as you sound like an experienced flyer.

Have fun and keep me posted, I'm interested in your building choices and how they work out.