I have an Eagle II that I use for training for the last 3 years. I installed a ST GS.40 on it and an 11x5 apc prop. Here's a video of it. It hauls the plane really well for a $49.00 engine. I could go a 10x6 prop but the 11x5 helps slow the plane down some on landings.A Magnum .524s would be perfect for this plane. Anylarger prop and you'll be having clearance problems.
http://www.rcuvideos.com/video/Eli-and-Eagle I would save a 70 4s for a more aerobatic type plane but if you want , you can install a 70 .4s, just way overkill .