trickworm, how long had the cooker been running when you took your readings and were you reading door therms or actual grate temps with a digital or grate thermometer?
The R/F I built for the Smokin'Ace's takes about 1.5hrs to level out this is actual grate temperature not door therms. Their differences run about 5° to 10° difference left to right. but before she is all up to temp the grate therms go crazy.
I never trust door therms on a cooker they could be an easy 30° off from the actual grate temps depending on the cooker and its size.
I agree with Tom give her a few more burns and get four oven grate thermometers place them on the grates in various places and make notes, give the cooker enough time to equalize and heat the whole plate watch your door therms in relation to the grate temps and take note of the difference. This way you will know when your cooker doors are at say 200° your really at 225° or even 250°.
I hope this helps.