RE: 50cc Plane?
It's not quite that complicated. I sent DA a message asking if they had a header to work with the DA50 and the pipe on a Katana. This header is sometime referred to as a question mark header. This is the response I got from DA: "We do sell the header that Aeroworks used in the 29% Katana. The header is a mtw double bend 50mm drop header and costs $36.00 plus shipping."
Just contact DA and they will help you.