>     Dont forget to factor in the variation. The amount to add or subtrack
>would, of course, depend on the year of the vehicle in question and the
>exact lat/long of the vehicle when parked. This information will be found in
>the legend of any good chart.

Could be important. If rotation is in the correct direction it could help
swirl the POR-15 into those hard-to-get-to parts of the sills as you pour
it down through the holes you drill in the floor edges.