I am about to drop a piped PA40UL into an RSM Oriental Plus, which is about 605 inches. Model is ready for clear coats and then (ugh) buffing. Anyway, a Dee Rice design that reportedly flys very well. Designed for piped 40 from ground up, not retrofitted. The model was recommended to me by a top West Coast stunt guy. Excellent quality kit, as usual from RSM. If I can get the picture from cell phone to computer I will post a photo.
I understand that Bob Hunt may have some Randy Smith designs scaled down slightly to about 600 inches, precovered wing and tail pieces. Of course need to scratch build the fuselage in such case to get appearance points.