Mods for the ultimate:
Definatly 2 servos in the bottom wing, standard servo's are fine.

A 90 4C will work fine, I used a 91FX, I've heard that alot of people use a 120 4C.

Toss the lite ply ribs that have the mounting for the end-plane struts and make new ones out of 1/8 5 ply.

Make a doubler from 1/8 5 ply to strengthen the area where the Cabanes bolt into the fuse.

The steel wire that secures the top wing to the Cabanes is a clever set up and holds well but mine made a horrible rattle from engine vibration, had to do surgery to convert it to bolt onto the cabane.

Use 5 ply 1/4 inch for landing gear mount and reinforce with epoxy and tri-stock. Use aftermarket landing gear, I got mine from Moose Carbon-fiber for about $25.00. I also glued balsa to the landing gear, shaped it to an airfoil contour and covered it.

Use 1/4x20 nylon bolts for bottom wing mounting, I used 3, 2 in front and 1 in the rear. Use basswood in the wing in this area so bolts wont smash the wing when you tighten them.
The stock metal bolt set up is known to loosen in flight.

Use 4-40 rods from top to bottom ailerons.

Try not to add weight, I used 3/32 balsa to fill the large holes in the fuse, and basswood for leading edge of rudder and lower part of rudder, this contributed to having to add 6 oz of lead to the nose.

reinforce area where tailwheel bracket bolts to fuse and dont use the stock tailwheel, it can tear out or the rudder, I used a sullivan tailwheel bracket.

I heard of a book by Hayes called "building bipes" that has some mods just for this plane, wish I would have looked at it.

My plane came out at 8.5 lbs. Flies great, good power. With the recomended elevator throw for first flight, the plane barely made it off the ground, using the higher rate would be best to start with, aileron throws for begining worked ok.
If I think of anything else I did I'll let you know.