12mm sounds high to me , I just rebuilt a table that I built quite a few years ago and I set mine up with the bottom of the men 5mm off the playing surface and it plays perfectly.
My table now has tornado men on it, I would have to guess that not all tables are the same as far as height above the playing surface depending on the type of men/players.
If you have more questions feel free to ask.
Here are a couple of pics of my home built table.