[jome]

Hmm, never thought of that, but I tried it and I can do it too (I'm assuming you're talking mouth open without the tongue block).

I guess it is not a pure Frenzel, because your soft palate must be down to be able to do this. I guess the pressure is generated by contracting the throat somehow...

I'd say your technique is probably better than a valsalva, but to be able to utilize the mouth fill you need to learn to control the soft palate too...