RE: Converted Y/A F-16A to from DF to pusher
How is the exhaust going to get out of the plane? From the looks of it, air flow coming in the inlet duct will hit the end of the pipe, increasing exhaust backpressure and costing you performance. Also everything aft of the pipe outlet will get coated with exhaust residue and be a real pain to clean. I suggest that you consider a Byron tuned pipe, which reverses the flow and exits exhaust in the rear.
Joe