3.5" is only 2.5% of the 138" wheelbase. This means 2.5% of the camper's weight will be removed from the front axle and added to the rear. For the 2600 lbs you listed, that's only 66 lbs. If that's dry weight you can calculate using the 2.5%, assuming the camper COG doesn't change significantly when loaded.
Many on here will say the camper COG must be at or in front of the rear axle which just isn't true. I've even posted GM's camper loading guide in the past where the COG can as far back as the tailgate so long as the relative loading of front and rear axles met a certain ratio. I think the principles would apply to any make.
Personally, I'd have no problem with it.
If you're still concerned, add a front receiver hitch for cargo and pack your heaviest stuff toward the front.