2013 Sprinter DIY 144WB, Portland OR
Yes, the sandwich is roof ribs <> headliner <> fiberglass angle.Hi George, Thank you for the link to your pictures.
Are the Fiberglass angle pieces installed directly on the ceiling mounts or did you install another T-slot on the ceiling?
I am wondering if I can eliminate the T slot under the 80/20 completely to bring down the cost but would rather install it if it helps provide better support.
You can attach lower outer beam directly to sheet metal like I did my 1/5” x 0.75” 80/20 profile using for example bolts and t-nuts. But I would suggest to place a thermal break like 3/8” thick fiberglass or other insulating material to prevent heat transfer. Aluminum is an excellent heat conductor. Dave learned this first hand and shared it on this forum a while back, I followed his recommendation with thermal break.