ok I don't know what makes a good working propane burner. Mine is modeled for oil, not propane, but burns propane just fine.
My ID is about 1.75". When I start I set my high pressure regulator at 10lbs. I let the burner naturally aspirate through my blower arrangement. I run a spin vane because it makes a definitive difference with the oil aspect of operation, it also makes for an effective brake for slowing flow while burning propane. Lastly, my burner may be 12" long and the propane feed might be 8" from the mouth of the burner.
My short guess is you need more propane. You need a high pressure regulator.