Go FOR IT !!!!
I only have one stack, the pipe is 4" from the turbo, through the ebrake, to 4" flex to 5" through the bed to a 6" stack. The sound at idle and under throttle is beyond description. Yes, it is loud, but it's a 'good' loud, if that makes any sense

. When I activate the BD brake, the sound is very close to a real Jac. brake equipped big rig, when I deactivate the brake, it sounds like I have air brakes (if I had a dollar for every time someone asked me if I had airbrakes, I would have alot of dollars

). When the truck is at idle with the ebrake on, it makes a very distinctive 'HSSSSSSSS'. Kinda sounds like a 4 ton cobra, ready to strike.
I only see one real downfall to the stacks. With the large injectors and the smoke they put out, I get a good soot shower at start up. Not a problem on the dry days, but if the truck is wet from dew or rain, it sticks like glue to the truck until I wash it off

. Small price to pay for all of the other benefits IMHO.
Scott W.