FWIW on my 99Hemi the headers are touching the the diaper. DJ safety added some heat resistant material where the headers and diaper make contact. This is a big tube header with a very wide engine but I do have a rack. IMO it is piece of mind but there are some cars that make it near impoosible to accomplish.

I look at a lot of cars when we are divisionals, we have plenty fo time ya know. Anyway I see a lot fo the SS cars using pans instead of diapers. Especially with the FE Fords, 66-7 Chevy II's and a number of Mopars. The only concern I have sen is they can hang up in the lights as some of them are VERY low in front and cast a "Shadow" on either side of the front tire. I had the same issue on my big tire car with a one size fits all diaper. At some tracks it would hang up in the light and give horrible reaction times and and quick ET's. Alsmost got me at a National Open but my opponent redlit.