There is no doubler on the bottom of the rear wheel well on coupes or roadsters. The doublers were probably added by someone to cover rust-outs, which are quite common. The quarterpanel was wrapped around the subrail about an inch at the bottom of the fender well. There were slots cut in the inside to allow water to drain out. I have some pictures of how I repaired the rear fender wells on my 28 coupe if you need pictures, which are very close to a roadsters fender wells.
Rusty Nelson