Actually, I used that picture of the burner because it was the only one in which the burner details showed well. It was around or under 1 psi. Mostly, I've played with 2-5 psi. 15 psi is obviously pretty intense. When we get back from vacation and start heating metal, it'll be easier to judge performance.
The choke is easy to adjust from rich to lean. Rich is only open 1/2" to closed. Flame looks "limp", with greenish tinge. Around 1" open seems neutral and bright blue. Anything more, and the flame is still blue, but gradually paler.
Tell you what, I'll post one of the out of focus photos which'll give you a better idea of the flame. It'll be in the dropbox as newforge_11.jpg. It's a crappy picture, but shows a flame beginning to lean. I think it was 5 psi, IIRC.
I wish I had more time to play with it, but have to get the boat ready for the trip south.
Thanks for your input, Ron.
Pete Keillor