J. Phil Thien's Projects

I have the ever popular HF 2HP.  Preparing to build my version of the "Thien Baffle" after 2 weeks of research, (while I recover from hip replacement surgery).  I plan on using threaded rod between the top and bottom plates so I can adjust them for max efficiency, keeping in mind at least a 1 to 2 inch separation between the bottom of the inlet port and the bottom plate.  My question is, has anyone already done the research trials on this and know what the best separation between the 2 plates should be?  Also I've read that the thickness of the top plate used ranges anywhere between 1/4" to 3/4".  Does the thickness make any difference?