Squats, we built band anchors so they're anchored directly under the bar, and with the bar moving in a straight line up and down, they remain in position through the squat. We hold the band anchors down with 100 pound plates. Project can give you the specs on the anchors, but I think they're 2 x 6 or 8, and there are 3 or 4 of them put together in such a way the the middle is raised and the front and back are on the floor. I'll try to get a pic.
I don't use bands for GM's, I use chains...
For bench they get looped under the power rack, threading one end through the center of the other end, then up over the bar. Depending on the band, you could choke it the same way on a low pin.