how to mount wheel tubs

[Turbo6Justin]

I don't have a lot of time to search anymore but did take a look and couldn't find what I was looking for. Like many my rear fenders are pretty rusty and I am going to start working on them in the very near future. Because of where the rust is and future plans I am looking at throwing in wheel tubs instead of rebuilding the fairly involved stock wheel wells. My question is say I buy some summit/jegs wheel wells or a bead roller and build my own how do I attach them to the outer body skin? I know this is a silly question but I have never paid close attention when I have been at the track. I am a competent welder but my concern is if I throw a 31"+ well in there obviousely it is not going to line up with the radius of the stock opening. But if I weld it say, 3" inches from the lip all I will have is a single unreinforced piece of sheet metal flapping in the breeze. Pictures work great for me. please help.

Justin