I have one that I took the time to fill with DAP lightweight spackle based on a review on EMRR. I made several rounds of sanding and patching until I was somewhat satisfied.
The only thing left was to mask and paint the red lines. I bought waterbased paint just for the job. I painted one side and the blue painters tape I was using pulled up the styrofoam with it. I said screw it, I just want to finish this thing so I can fly it and turned the rocket over to try to paint the other side. Thats when I snapped both tailpieces – one at the joint, the other one in half and at the joint.
Frustrated. Check.
It is in a bag collecting dust. I was going to repair it eventually and probably run into the same problems. So annoying because you see the great pic on the box and you read "E-Engine" and the little kid inside you goes, "hehe sweet." And then you buy it, take it home, and open the box to realize it is total crap.
After reading this I am interested in trying to fiberglass for two reasons.
1) Never glassed anything ever. If there is a rocket that is worth the effort, but the end result isn't important, this would be it. I'm either going to fly it or trash it.
2) I've spent $60-$70 for the rocket and materials plus time and I don't know when to fold 'em.