I thought the fender welting issue on a pickup boxes for 28/29 model A's was settled. I believe there was a thread sometime back that came to the conclusion that there WAS welting between the rear fenders and the rear of the splash aprons/pickup box. Maybe the very early 28's didn't use any welting - who knows. I hate to rehash this, but I thought it was a settled issue. See:
https://www.fordbarn.com/forum/showthread.php?t=37697
Rusty Nelson