I have a PCC 48" cooker with and insulated firebox just like the one described. I have never had that problem. I run with both exhaust stacks wide open. I start with a chimney of charcoal and then a small hot fire with splits of oak or hickory for the remainder of the cook. I preheat my next split on the other side of the firebox away from the fire so that it ignites right away when added. I manage the temp with tinkering with the air intake on the firebox (no guru). It is a very efficient cooker and doesn't take much of a fire to run it at 235 to 250 degrees once it settles in. I usually allow about two hours from start up to meat on the cooker so it is nice and stable. Sounds like the guy you talked to is using way to much fuel and having to choke his fire to maintain his temps...not a good idea. Sounds like he should have bought a BGE instead of an offset...
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Peoria Custom Cookers 24" x 48" Trailer