Greetings - I just picked up on this post and see that another brewer is having an issue with a homemade burner. I have spent about 35 years in my career servicing burners in HVAC equipment and even with that experience, I still would walk away from a homemade burner.
So, jtoots said it best - "I personally wouldn't mess with it". A good quality propane burner is not that expensive as compared to the damage to life and property that can be the result of an improperly engineered burner.
Good luck!