We have the 2017 840SB model much like yours. It has every option except streetside awning, microwave, roll over sofa and DVD and we have the smaller Coleman Mach 8. Actual dry weight is 3360.
I store sewer hose in the pvc pipe and fastguns and awning hand crank in rear bumper storage.
On second trip I scraped against a branch and damaged roof on the corner just like your looks. New roof! I know better now, had no idea it was that fragile.
Check all the fasteners and the sink trap for being tight. Many of the screws on our unit were not tight and put in at an angle. We also found incomplete caulking work in many places. Camper leaked 1st trip at the driver front jack support because of incomplete caulking, sloppy work.
Have already replaced the lp Regulator, the front sliding window (leaked when traveling in a rainstorm) and the insert trim on front of camper. Pic shows screw put in at 45 degree angle underneath trim that sun destroyed in less than a year.
Mods made were to put down hypervent material under a new memory foam mattress and remove bunk front over dinette and put up cargo net. Amazing numbers of things can now be stored up there with out being confined by the doors I took off. I'm going to remove the doors from the 4 bedroom closets and put wire shelves in. The doors open into the ceiling where the corner hits once it's opened far enough to hit the tapered part of ceiling. It would have made more sense to have door open against wall instead.
Once you finish building the unit for the manufacturer you will have a solid camper to enjoy. We are very comfortable in ours.
Congratulations and happy trails...