Bipes are no harder to fly than any other type plane. What is more difficult is that you can set them up wrong and then they will be hard to fly. I have built and flown at least 15 different RC bipes and all fly very well, some are just like a trainer. The main thing is to be sure the wing incidence is set properly. Pay particular attention the that. Start off with the manufacturers recommendations and, if you have problems, start varying the incidence of the upper wing. On at least 12 on my models, all required that the upper wing be set 1.5 degrees less incidence than the lower wing in order to fly properly. Of course engine off set is important and be sure that the CG is per plan or slightly ahead of the recommended point.