RE: LR-1 Pylon racer
Rear exhaust should work fine. It'll take a little more work for the motor install. You'll have to cut out enough clearance from the cheek cowl for your header and then fiberglass a piece of 1/32 ply or something to button up the hole and tie the structure together.
The wing is not in the way of a mini tuned pipe so you're good there.
This plane flies really sweet as long as it is not overweight. The electric versions over 4 lbs showed bad stall characteristics.
You should be under 3 lbs with the MVVS.