Guys, thanks so much for showing me how you handled this on your cars.
Defdes, the step by step photos are worth, well, a few thousand words I guess.
Keith, I'd seen a more distant photo somewhere else of your installation but couldn't see the detail of the mounting-holes. Again, your photo helps a lot. And Julian, yes the structural integrity of the area is also part of my concern. If I can work out a way to use the original 3 mounting-holes (as Keith did), cutting as little as possible (as Defdes' work shows), I think it'll turn out well.
Again, thanks one and all.