I have the Spanek vertical roasters set, and they work great. Roasting vertically decreases cook time, and improves the skin texture. I've haven't tried crisping up the skin in the Bradley. I have a vertical charcoal smoker that I smoke/cook chicken at 300°F, and that temperature does not crisp the skin, but does render the fat in the skin so that the skin is bite through. I haven't tried it at 320°F.
I have tried dry brining with salt and baking powder (using a recipe over at Serious Eats), that does improve the texture and gets the skin crisp using high temperatures, but I haven't had success trying to crisp the skin at lower temperatures. Just don't use too much baking powder, it will give the chicken an off metallic taste. Other methods are pricking the skin being careful not to penetrate the meat. That helps the fat render out. Roasting vertically helps the fat render. Some say using corn starch in your rub helps crisp the skin, but I haven't tried that in the Bradley.
You can change any setting at any time, you just need to disengage the "Child Proof Lock" by holding the rotary knob for several seconds.
PS
I forgot to mention to leave the vent wide open to allow as much moisture as possible to escape from the cabinet.