Hobbico's Sturdy Bird II, when powered with Super Tigre's .51 is the ultimate trainer, with a few modifications. First, cover the entire wing with the strapping tape before covering and lose the thrust angle on the fuse.....just cut it straight across! This setup allows the plane to fly inverted without effort, and the power is great! I can't imagine why they would suggest a .25 for this plane, but with a minimum of .40 you'll be pleasantly surprised. This plane is inexpensive and even though I've moved on to faster and more 3D capable craft........I still find myself flying the Sturdy Bird when I need to put a smile on my face. If you want a plane that can take all the punishment that a novice can give it.....try the Sturdy Bird II. I believe that the Sturdy Bird is one of the oldest ARF's out there too, so that says something doesn't it? You won't be disappointed. Have a good one.