Did you order the hand crimping one or the one that mounts to the spindle and rolls?
I used the one that mounted to the spindle and it was tough going on the front especially, the fender wanted to bow out as I increased pressure on the wheel. I ended up 'massaging' it with a small rubber/poly mallet to get the bend started as it had a hard time getting the 90* lip to start to bend. I was trying to figure out a way to brace a 2X4 against a wall and the outer fender so it couldn't bow but used the mallet instead, I'm no body guy so I'm sure others could do better, it'll be fixed before paint. My car needs paint so I didn't worry about heating the paint to save it.
It did make a huge difference though, my 225/60/15's on 3.75bs TTD's cleared after rolling F/R.
Jon