Missed your post, sorry for the delay reply!!!
Probably a good thing going with the 1200lb bars. Can't see you needing more than those, but the &00lb probably would be undersized.
How often do you think you will travel with a full vs empty fwt? Only ask because the DC can be finicky and may need adjustment when full vs empty fwt (unless tank is over the axles). Other than that it is a great system!
Do you have the 5.3/6spd in your truck? What axle ratio? If the 3.42, I don't see you having any issues power wise towing the 27 BH. With our '10 Chevy 1500 ccsb 5.3/6spd/3.42 4x4 towing ~7200lbs we had no issues here in Mi, even the long, continuous incline just north of West Branch on I75. Just let the motor breath and it will do its job. Our truck was ever so slightly loosing speed in 4th gear, dropped the trans to 3rd and I had to actually back off as I started to exceed about 70 when I looked down! We did have some stuff in the bed, probably put us over the gvwr of the truck by about 200lbs. That's the reason we now have a 2500HD, payload.
I was, and am still amazed how smooth the factory ibc works!!! Just is an awesome unit!!!! One thing you may need to watch is the stock tires in the truck. P rated tires can have what I call the "P rated wiggle". Due to the tw of a tt the sidewalls of the tires will flex some, and cause a slight wiggle. Almost like two people are pushing towards each other against the back sides of the truck bed, causing the rear to "wiggle" back and forth. LT tires will solve that, even if just LR C's depending on your set up. Air your factory tires up to max sidewall pressure (44lbs???) when towing.