Some of these machinists on here should make some mini-tips to match the ones on everyones transoms. Little slant-cut and straight-cut ones.
Most people run them out the side of the boat like a bildge dump.. If they ran them out the transom at waterline or below like an exhaust tip you'd have to put in one way valves or "flappers" etc.. Pain in the ass. However if ya really wanted a slanted exhaust tip, well then I know a guy that'd be happy to make ya one.
RD