I feel I have finally gotten good enough flying my Sig Kadet LT 40 that I am ready to step up to a low winger. I bought the four star 60 and am in the process of building it but I am having a difficult time deciding what motor to put in it. I either want the OS 91 Surpass II or the OS 75 AX. Does anyone have experience with either or both and can tell me which one would be better suited to this airplane? Also, I read a lot of negative things about four-strokes without any support as to what they are talking about. For instance, people say the maintenance on a four stroke is more...what are they talking about? What kind of maintenance? Thanks in advance for your answers.