I am planning to use a YS 1.40 in mine although I do have a Saito 1.80 already on hand that I could use and I'm sure would be great. I like both brands of engines, but the "pumped" part of the YS will make an inverted mounting of the engine a little more pleasant as far as running is concerned. I will not have to worry about fuel tank height in relationship to the carb. This can cause a problem on an un-pumped engine if the two levels are not pretty much the same and sometimes it is not convenient to get them at the same level. One can always use a Cline regulator if needed with an un-regulated engine and that will also work nicely. Have heard reports with the big WM Miss America that the Saito 1.80 is a great powerplant. Most of the gas engines in this thrust range are too heavy for this plane as around 32 oz. is a good target weight. Maybe this will give you some "food for thought".