Since I never mentioned any agency involved (and frankly don't know one way or the other), I don't get the distinction between PADI and NAUI here.
If you read the other posts I made, you will see his problem has nothing to do instruction. His neck size was just a hair larger than the range for the small neck seal and at the extreme low end of the standard neck seal range. They sent him the small neck seal, and he is finding it too tight. He needs the larger neck seal. If it turns out to be too large, he can buy a
neck seal ring that will make it fit and also make it pretty much leak proof.