Moving Rear Flares Up - How to attach

I'm cutting and moving the stock rear flares up. I know that most people use self-tappers to hold the flare on. I've read the write-ups and all that but I would like to hear from others too. Is there a better way? Can you get access from inside if you remove the plastic and tack nuts on the backside or something? I just want it to be mounted as strong as possible so it doesn't rip out if it gets caught on something. If self-tappers are the best way, which specific ones work the best? TIA.

Edit: Also, when cutting the rear up to the pinch seam and then folding the sides over, do you lose any structural integrity? Should I weld it in place once I've folded it over?

The stock flare brackets (stock flat metal) are basically junk after removed. I used 1" wide aluminum flat stock to make new mounts. I spaced the mounts at about 12". I used pop rivets to attach mounts to the flare and bolts at the body location.
I didn't hack to much out of my rears. Just went with the cut and bend method, leaving the pinch welds intact. No rewelding but I'm watching for any signs of trouble. HOH

I cut right up to the bottom of the holes, and then hammered it back as much as possible, so the pinch seam is still intact but I opened it as much as possible without having to re-weld the entire fenderwell. After hammering it over I started to weld it but I couldn't get the heat low enough and it blew through in one spot, so I need to get some smaller wire and use that instead. I chopped the flare right where it had the bend to conform to the body, but I'm still trying to figure out the best way to attach them or find a screw that looks tough enough to withstand some abuse (deep threads?).