A year or so ago, I bought a couple of hold fasts from Black Bear Forge. They are awesome and worked great on my temporary bench top (solid core door). However, now I have built a Roubo with a much thicker top ~4.75" thick. Now, these holdfasts aren't holding very well. If I get them to hold at all, I have to hit it just right and even then it isn't a great hold. I reached out to John at Black Bear Forge and he suggested counter boring from the underside to make the effective thickness less. The question I have is what is a good way to go about this? Any suggestions?