While I'm mainly a UDS guy, I do have an offset as well and it's a leaky bastard at that-prolly why I hardly ever use it!
While I don't have a lot of offset experience, a few things I can say is to seal up those doors and any seams as good as you can to help you hold an even temp. I also put some firebrick in mine to act as heat sinks to stabilize temps at it helped immensely. Might wanna run a water pan in there too to help keep moist and hold temp. I'm sure others will chime in with more insights. Good luck!
UDS'55&16, Akorn, Bar-B-Q Kettle, mini WSM, Drum Grill. I'm JD.