Sometimes it's hard getting anything bigger then a 60 in one of the Bridi designs. I couldn't get a .91 four stroke in the Dirty Birdy without bashing the fire wall/nose section so I went with a .91 two stroke and had to hog out the cowl to get it to fit. The motor mount had to be left in the plane but I could remove the engine. To get a YS 1.10 in a Kaos I had to build the cowl around the engine. The Kaos had a bigger fire wall then the Birdy and the cowl was one I could remove. There is a 80 inch 120 size Kaos, I used an RCS 1.40 in mine, plenty of room for an engine in that one. I have flown every size Kaos I know about and they all fly the same. The smaller ones just have a faster roll rate and the bigger the plane the more stable.