Skim coat application

Graveyard cars does that too. You are basically eliminating and then recreating every body line on the car :(

Lots of pro body guys will tell you EVERY car needs one to get straight panels but this is BS because my 73 has factory metal with no skim coat and is pretty damn straight.

The main problem (besides all that) is that it absolutely WILL come apart from the metal eventually, unless it's almost never driven and stays in a climate controlled environment.