Motor plate question

Both of my cars with motor plates have the frame mounts welded on. But, I don't see why you couldn't bolt an angle mount to the frame, with a couple grade eight thru bolts on each side going all the way thru the the front subframe. I'd double nut or cotter pin the bottom of the thru bolts.
My one car has an old hurst front mount setup, (steel) and a steel mid mount plate, with an add-on trans crossmember that probably isn't necessary..... but I built one anyway.
My mopar has a pair of elephant ears that I made, and they work..... but if I was doing it again, I'd buy the AR engineering one piece plate.