I read this thread carefully, because I too want to add a couple of batteries in the storage box next to the battery box of my Greyhawk 29MV (class c). I went to the coach, crawled under, and found that my storage boxes hang from the floor. I called my dealer, and the parts fella stated the storage boxes on my coach are all rated at 150 lbs total capacity per bin.
The two AGM 12 volt batteries I'm looking at have a total weight of 130 lbs. I have considered running some steel straps from the floor, under the storage bins back up the other side to the floor for the assurance that bumps and the weight of both batteries will not jar anything loose.
What do y'all think ...???
From Cajun Country
Jayco 2016 Grey Hawk 29MV Champagne
Toad - '16 Subaru Forester (Pearl White - manual transmission)
Blue Ox (everything) for the TOAD
EEZRV TPMS System