TXLX says
If I had it to do again, I'd get rid of the 3/4" pipe nipple & ball valve setup and go with a rectangular slider vent. Adjustable racks are nice, but I'm happy with my fixed. I can always bolt some 90° angles inside if I want to go up or down.
I believe my top rack is 8" from the top of the barrel and the lower rack (mainly for my drip pan/diffuser) is 4-5" below that (just below the top "waist" of the barrel. Obviously you can go higher with a weber lid.
agree mostly except instead of slider vents on bottom just 3 one inch holes, save ur money on ball valves and just use heavy duty refridge magnets u already have hanging all over the place. my lower rack is 9 1/2 inch from top, my top rack is 4 1/2 from top, flat lid. wish it had a weber because can't do thicker cuts.