I think your talking about the exterior side wall. I have never touched sliding above the metal plate cover. But, I just used my IR gun on sun exposed siding it is 110f air temp is 75f. I know the metal cover gets dam hot at the exhaust area.
2013 24RKSWE (27ft TT) Cougar 1/2 ton series
2013 Ford F350 4x4 CC 6.7 engine, 8 ft bed 3.55 rear end lariat package
Retired from Oregon State Police in 2011 than worked another 9.5 years as a small town traffic cop:
As of 05-2020, I am all done with 39 years total police work. No more uniforms for me.