I have the pb 033 diesel's "Big Daddy" the GB 5.4 cc long stroke side port. The original GB by Gordon Burford in 1947. Gordon and David Owen made two small production runs a couple years back of this design. One of my favorite diesels. Easy to start and happy with a 14/6 prop in my 80 inch Playboy Cabin with R/C. Lately I have been thinking of a U/C model for the GB. I have not flown U/C since 1969. I would probably get dizzy and fall over trying to fly U/C. !Jack