its a Oracover plane it will wrinkle even without the exhaust heat ;-).
dont worry so much , the heat is normal and you will suffer also from the "oanda"effect where the heat is drawn towards to fuselage in flight.
so slowly after time you will see some discolour comming.
as for the cowl ... yes it gets hot.
i always keep a high idle on the ground , and just before turning engine off , i spool up to 25% then turn it off , it will cool down much quicker.
get that bird in the air!... ;-)