I've been thinking about getting a suppressor.

Here is what I currently understand:

1. Need to apply to BATF and pay the $200 "tax" for the can.
2. Need local LE to sign off on it.
3. If/When approved the same can can be used on multiple weapons of the same caliber.

Here is what I am interested in doing. I am thinking about getting a can for .223 cal and also being able to use it on a .22 cal and a .22 Mag. It is my understanding that the size and suppression ability of one for a .223/5.56 would be a bit of over-kill when fitted on a .22LR/.22 Mag., but that shouldn't be too much of a problem...right?

Am I missing anything?