I had one with an OS FP-25 for several years. It does fine with that motor and will fly the plane, although if 3D or intense aerobatics is what you are looking for, then you probably should go bigger. If you look at the weight between a Seniorita and an LT-25, the flying weight for a Seniorita is 3.75 lbs and the flying weight for a LT-25 is 4 - 4.25 lbs. There is an article about the LT-25 in an old RCM magazine and the guy who wrote it used a Royal .25 in his and it did great. Larger engines (> .25) are just not needed.