simonwalther
My advice is to take the most conservative course of action. That means a visa and TSA registration.
I considered the less than 18 hours routine (advice from US Consulate Services in London) when I did a Commercial certificate but in the end took the visa route to be on the safe side.
It meant I had to go through a narrower range of schools but that was no problem.
But in the end, I wanted to be safe rather than sorry.
Overly cautious maybe.