There is a patent on the website ( Valor?) for reducing underburning by drilling holes in the inner cap and the tube above the jet.

Anyone know if it is worth trying?

Actually, Optimus used the same principle on its silent burner from around 1960: 9 holes drilled in the top of the inner cap and four holes drilled in the central tube, under where the inner cap sits.

Actually, Optimus used the same principle on its silent burner from around 1960: nine holes drilled in the top of the inner cap and four holes drilled in the central tube, under where the inner cap sits.