A pitts style muffler is one way of fixing the problem. Not sure what brand of engine you are using, however some of the manufactures have an extension available for the stock muffler that will allow you and extra inch or two for the muffler to be on the outside of the cowl. As for engine cooling, the golden rule is 3 to 1. That is for 1 inch of intake, 3 inches of outlet. If the head is hanging out of the cowl anyway, this is not usually an issue. Hope this helps and Good Luck, Dave