For sure replace the push rods, the nylon ones in the kit react a lot to temperature variations, and expand and retract a lot.

for the fin/fuse joint, I did the same thing small fry did but with 3 5/64 steel rods instead of dowel. also, make sure you blend the fin to the fuse before doing anything, so there are no gaps

put push rod supports on all the fuse formers aft of the servo tray.

put a piece of 1/2inch triangle stock on the bottom of the firewall/fuse joint, this helps for those not so great landings a beginner sometimes experiences.

file a flat spot on the nose gear rod where the set screw touches it

this is a really great flying airplane, and aside from replacing the push rods and reinforcing the fin/fuse joint, you really don't have to make any changes.