With the Bradley, you will find temp variances not only from top to bottom but also front to back. If you want to try and ensure they arrive at the end point at relatively the same time (highly unlikely but one should always try to have goals ), you want to make sure to rotate your birds during the smoke and do it again by not only moving the birds top to bottom but also front to back. With my Bradley, I found the temp was highest down low (this makes sense since the smoke generator is closest to the bottom rack but also because the heating element is down at the bottom on the back of the smoker). When doing poultry, I always had good luck by melting butter, dipping cheesecloth into the butter and then draping the bird with the butter soaked cheesecloth. You'll find that in the Bradley the skin of the chicken will get rubbery otherwise. I also liked to throw it in the oven to crisp up the skin a bit more afterwards but I'm one of those that loves the skin as much as the chicken.
I concur with the others with remote thermometer in every bird if possible. If you're looking, you ain't cooking. Also, realize with three birds in there, it will take the Bradley some time to get up to temp. Bump the temp up higher than you want to get the temp up faster and then bump it back down when you've reached your target temp. Hope that helps and welcome from one newbie to another.