I'm not trying to sound harsh but it seems that when anyone makes a UDS and deviates from the simple kiss method (keep it simple stupid) and then has problems they always wonder why. You say you have a 3.5" exhaust. K.i.s.s. method calls for 2" or eight 1/2" lid holes. Intake you say five 3/4". K.i.s.s. is three 3/4" holes for 1" nipples. And when you start your fire you bring it up past 300. The k.is.s. method calls for catching the temp on the way up not trying to bring it down to stabilize your temps. Hope this helps some. Look at one of my last ones I built. Yes it has a lot of little add ons but if you look close it's still a k.i.s.s. UDS. 2" exhaust with three 3/4" intakes. I'm on build #15 coming up this week and everyone of them has run perfectly because I don't drift from the k.i.s.s. method.