Make sure your fan pushes enough cfms to heat the unit. Sorry, I don't have those facts and figures, but I'm sure pitvipers' site does if you look in their fan section.
I would just rotate the lid so the exhaust is opposite your fan. Unless you're a donkey like me and use yours inside, it shouldn't matter if your lid is rotated to one side or another.
If you're going to just extend the bung with pipe for exhaust vs drilling holes (that's what I prefer, using the bung) then keep a piece of 4" pvc pipe a couple of feet long to place over your bung extension for days with low winds. This will increase the natural draft and help take some of the load off of your fan..
Edit: when I say "use mine inside", what I mean is that I have min hooked up to a rooftop exhaust system in my heated garage so I don't have to deal with cold or rain or snow :-)
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