I'm pretty sure the FIS rules are now 50mm for the combined stack height of the ski thickness and the binding stand height. This was 55mm a few years ago. They have also lowered the approved height of the bootboard at the heel of the shell.
I know that the FIS rules technically don't apply to us, but I ran most of my ski setups at 55mm a few years ago and I've also dropped them down to the more reasonable 50mm as of late. This amount of stack height still is quite noticeable and definitely increases the sensitivity to tipping angles.
When hyper-carving was still the rage in Europe (I think it may still be in some parts) Tyrolia had come out with a 23mm plate! They came with "dragon brakes" that were extra long so that the brake arms would still contact the snow when released. I still have two sets of those plates (brand new) because I just needed the dragon brakes for my setups that had 55mm stacks. These plates will still mount the standard Head/Tyrolia bindings (screw locations haven't changed). So if someone wants to test out a 23mm plate let me know - you'll just have to pay for shipping.