So my best friend’s son is a structural engineer, and he and I are talking about designing an ultralight. We were talking about which engine to use RE: power/weight ratios, engine weight, etc. and I mentioned that I see a lot of folks using the Rotax 503, but that I didn’t have enough information to offer an informed decision. Does anyone out there want to offer a few pro and con bullet points about this particular engine? Especially if you have experience using this. Thanks.