Buckland,
I've had my Duramax Colly for about 6 weeks now, a 4x4 CC SB. I have figured the mounts out, and just need to decide between the Swift or Fleet shell. This last weekend, I made a test to see how the springs would react to 1000lbs. I have 3 spare tires/rims for my FMTV, they weigh 340 lbs each,all told, about the same as a modest FWC.
. The truck dropped 4" at the rear and up 1 1/2" up in front, and as you can see, all the weight is behind the axle, and a camper would put a small amount forward. I have ordered Air Lifts for it. I know they'll be needed to retard the rebound of the stock springs.
Also there are 3" antennas for the Colorado on eBay
And as I did with the Kestrel, I'll make a forkliftable riser on the camper for quick r&r.
BTW, I tried to get FWC to make a "proper" camper for the Colorado, which amounts to a narrow version of the Raven or Hawk, but said no. I would love to have the 6" of extra height in the door.