Definitely look at the other threads, but here's a summary of what I suggest after having built and flown a couple of them.
1) The center spar is fragile. I recommend beefing it up by gluing additional spars on each side. You might also consider rigging up some way for the rocket to return horizontally so it doesn't land on its nose. I tried to do that without success. It is hard to rig up a harness that won't catch on something.
2) Replace the motor mount tube with a standard 29mm motor tube. The included motor tube doesn't fit modern motors.
3) Replace the parachute with a thin-mill parachute. There is very little room to pack the 'chute and shock cord. A thin mill one takes less space. But it can be annoyingly slippery. You might consider replacing the shock cord with a long length of braided Kevlar, but I haven't tried that yet.
4) Explicitly follow the instructions for packing the parachute and shock cord. Do not wrap them around the motor tube. Zig zag them as described in the instructions. Don't ask how I know that this is important.
