Two interesting facts about toppers. Especially fiberglass.
1. Your gas mileage will decrease.
2. The weight helps with traction on the rear wheels significantly in the
winter.
I can confirm both of these.. 2500HD 6.0L gas w/ARE topper; definitely weighs more and affected MPG by 1/2 to 3/4 MPG. Had to take topper off at one point & send in for repairs and confirmed the difference.
I have an ARE topper with crank out side “wing” windows. While I don’t have a center slider, I wish I did for a little better ventilation in the summer; temps under my topper, with both wing windows open run about 10 degrees higher than ambient (I think a lot of it is radiated from exhaust through the bed) when running down the highway pulling our 35′ bumper pull camper.