Ok running batteries in parallel I get but how much difference in voltage is ok between batteries b4 one is weaker and causes the ‘good’ battery to drain.

Just got my Lund impact two weeks ago, thinking on putting a helix 7 in it but HOW? Do you know if Ram makes a mount that will fit on the mount on the dash, such an unusual mount, and if there is will it fit the helix 7 without interfering with the windshield? what were they thinking when the placed the mount so close to the windshield?