Location: The mountains of Scottsdale, AZ, and the beaches of Maine
Posts: 10,088
My guess is that there are two purposes.
1. To spread the load of the unit's weight across the roof structure.
2. To keep you from hitting your head on the inside parts.
Bill
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2020 2720QS (aka 2720SL)
2014 Ford F-150 4WD 5.0L Bill's Tech Stuff album