I've built a Swallow EX, you should look through the other threads that have been on this plane. Some people have had various problems; the most frequent occuring being problems with undercarriage and the fuselage breaking. I haven't had any of those problems, or any other major problems (other than radio failure, it landed in a tree, just had to replace a bit of covering and some balsa a few places in the LE of the wing!). How much does that engine weigh?