I've never used an extended intake on a UDS, just a hole with magnets, so can't comment on height of valve (but have read of issues).
However, I can say with four 1" intake holes 2" above bottom, I have no issues keeping temp, even high temps. I can maintain 375 easy with 2.5 out of 4 holes open. Wide open, and starting with more than 12 briqs, I can do 500 and cook pizza all day long.
Of course I burn through a lot more fuel, but it's fun playing with fire, so I don't mind.
Modded Brinkmann Gourmet. Basic UDS. Rescued 22.5" OTS. SJS Mini-WSM. Stubbs. B&B Oak Lump.
Cannondale 2009 F8 (for burning off all the great BBQ)