I have a Funtana with a YS 63 and I have the cowling on. I have no problems at all with cooling the engine. Sometimes people don't feeli like putting on the cowling since it's a pain and sometimes they get banged up and they remove them. But there is no problems with cowling on any plane as long as you have large enough cut outs at the bottom rear of the cowling. A rule of thumb I've heard is 3 to 1 (outlet area to inlet area). The Funtana looks a lot cooler with the wheel pants and cowling. I have one that has them both and another that has neither. They look kind of ugly without it.