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I've been thinking about my first build, and reading all I can find on the various buffer weights/systems and now I find that (DUH on me) that the gasport size would have a major effect on the cycling of the action. I really want a 100% reliable weaon, and one that doesn't beat itself to death. All helpful hints and unique snide  remarks appreciated.

I also posted this in the general disscussion area for which I should be shackled and dragged

+1, got the same question. Got my lower completed, deciding in M4, Middy or Rifle length.

I wouldn't worry about port size too much unless you plan on modifying a factory barrel's length.  Rifle length operates at the lowest pressure, carbine at the highest.  In researching my build I found that most of the "fixes" used to slow the cycling or improve reliability of the AR revolved around problems that arose because of carbine length gas system.  In midlength and rifle length, these fixes appear to be unecessary for the most part.  Although the carbine system has been refined to the point that it is reliable, I personally consider the midlength to be perfect for 16" barrels.  FWIW my midlength has been utterly trouble free using the standard buffer and springs and whatever size gas port that Rock River spec'd for their barrels.

I used .84 on mid length 18 barrel and works fine.