Firm Feel upper control arm interference problem

Yesterday I did a test fit of my Firm Feel upper control arms on my 66 Barracuda and there is an interference problem with the frame brackets on both sides. See the attached photos. I guesstimated how much I would have to remove and marked it with a Sharpie. Anybody dealt with this? FF says to trim the bracket for clearance. I'm concerned about weakening the bracket.