1.  Screw and silicon left-over stainless steel firewall material to the fuselage.  Maybe put some spare fiberfrax under the SS.

2.  Construct stainless steel "shield" with tabs at each end and use hose clamps to hold it on the exhaust pipe.

3.  Find out why there isn't enough air leaving the cowling to avoid this or whether this happens only on the ground from radiant heat.  Anyway, try #1

Scott Krueger
LNC2 320 N92EX, Only have seen 235's from a distance.