[rickst29]

The ratio of watts per pound is really good, and a panel iike his will fit on the rear of anything '2720 or larger'.

Panels of this size are set up with two mounting holes along each long edge, and those holes are not near the corners - like Jim's photo, they usually have about 15% overhang towards the short sides and only 60% of total length between the mounts. That allows for 4 mount points (rather than 6) to be more than sufficient.

On a normal roof installation, a single long pair of horizontal rails is use to mount multiple panels in a vertical orientation. I agree with Jim that a panel that heavy, using just 4 Z-bars, needs to have the Z-Bars held through the roof with SS screws and interior washer/bolts (not just VHB tape). Jim's additional use of VHB between the between the Z-bar and the roof further improves adherence and water resistance. With screws, the screws themselves and the washers on the inslde ceiling can be also be set against the celing with 3M 4200 boat sealant, providing another seal from the inside as well.

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But, as Jim found, all the extra weight might require a torsion bar upgrade (rather than a mere adjustment). The panels themselves are also to big for Fedex/UPS. To avoid paying csotly truck freight, you will instead want to attempt purchasing a single "left over" from a local company which specializes in home installations. (The buy entire truckloads or pallets at a time, and often have a few "left over panels" from those bulk purchases.