Hello; I have an Ultimate which I flew with an OS 91, then a Saito 91. I had a Saito 120 in it first, but took that out for the 91 I thought that the 120 made the plane too heavy to perform the slow stuff I like to do, but still gave good (enough) vertical performance. By the time I had it all working as I like it, I had done quite a few modifications to it. I have seen the hog bipe fly with a Saito 80, looked pretty good to me, but not as hairy-batic as the Ultimate. I guess it depends on what kind of flying you prefer. I would be glad to have either plane. That Saito 100 is an awesome engine, I have one in my Funtana 90, it would power the Ultimate just fine for me. We fly at sea level here.