If you don't already have an engine try the Thunder Tiger 91 4 stroke. It runs a little stronger than the magnum. It will pull the same prop at the same rpm as a Saito 100. I have a Magnum 91 and the TT 91 and both are great engines. I have flown them both on my 4*60. I also have a 4* with a GMS 76 on it also. This engine pulls the plane vertical better than the 4 stroke engines and it is faster. I like the 4 stroke engines better because they sound so cool and they run flawlessly. The power is almost as good as the GMS engine but the vertical is not as good. A strong 91 4 stroke will pull the plane vertical really good though. Here are some pictures of my two 4*'s.

Rick