I have tried using the cast iron pan by its self and like the conical burner better. It allows me to run a varied drip. If I run the drip fast then a large puddle and more heat, slow then low heat. The cast iron pan does not allow this; the oil must fill the bottom of the pan before it can burn properly. My friend uses this process and when he opens the door you can see a ring of fire at the edge of the pan. My burner has the fire at the center. The burner is concaved at a 12 degree cone. It is made from 1/4 inch steel.
The few flow problems that I was having with my set up have been isolated. One is debris in my valve. The second is the valve it’s self, it has a very small orifice at the entry area. If this continues to be a problem then I have a new valve to replace it. As for the debris I have started to screen the oil when needed. I have also installed a 25 watt silicone heating pad, this helped with start up. So when you install your gravity feed system the higher the better and the warmer the better.
I have been burning the thing for two hours for since Sunday and started with 5 gallons of used oil, stuff that I have had in my shop for a couple of years. It is pretty thick and dirty, I will be glad when it is used up. I have about 15 gallons, a mix of 30 wt power train oil and 10 wt hydraulic oil, which is much cleaner.