There are likely much better solutions. How tall is the attic? Can you get something 6-7 foot high up there? If so a ScanTenna will work just fine....more details needed....73 Mike
As ka3jjz mentioned, there are much better solutions then a mag mount in the attic.
remember a mag mount located in any other location then on a vehicle, requires a ground plain
not hard to do, but just keep that in mind.