I would make the groove at less then 90* and deeper. Meaning that when a blade is placed in the groove the contact point is well up the blade's side as possible. This will better resist the flattening out of the blade as you bend it. Here's a shot to how i grab the blade. Not the best, it takes a lot of strength and focus, getting a 55mm rake was all I can handle. I have used a Hamil bender with it's rollered lever arm and it is SO MUCH easier to bend a blade. The drop out end of the blade is often held down by a small v block bolted to the groove's start.