Don't cut it yet.
This works for me. On the compacts, I remove the brake from the frame (drive out the pin in the top). Then I carefully flatten out the hook so the brake no longer has the curve in the bottom.
Without putting the top pin in, go about putting the brake, mainspring and plug just like before.... I align the brake in the back of the grip with the flattened portion inside the bottom of the grip by the hole for the plug. With mainspring and plug (and plug cut-out) aligned, I push down on them (the flattened end of the brake should slide along the outside of the plug) and insert the retaining pin on the bottom. On release, the flattened brake tip will hook and catch.
If you don't get it right on the first try, the brake tip might bend into a hook again and you'll need to start over. Finally, align the top of the brake with the hole in the top of the grip and reinsert the top pin.