The metal baffle will eventually assume the temp of the heat source.
Where are your thermostats in relation to grill level? I've seen some weird locations for them on some smokers even from the factory. It's good that you have more accurate t'stats now. I would mount a dial type t'stat no more than 3" above the grill surface maybe using 2 or even 3 depending on the size of your smoker.
The rest will be fire control. Add more fuel as needed but not too much etc. That rig should have a sweet spot. Once you find it, it's ON.
Just my .02
Weber WSM, Weber GA, Weber Spirit S-320
Charbroil Oilless Turkey Fryer
Wife LuzziAnn 1956 model.
Maverick ET-732, Superfast LSU Purple Thermapen
The Fun Never Stops at the BBQ Brethren Throwdowns
2013 Throwdown Grand Master. 1/2 of Team Paradise.