This summer I traveled from Houlton, Maine to "BusFusion" and back then
a week later I started a round trip to Tennessee.  The '85 Westy
performed well (about 4500 miles total).

I placed the Sirius magnetic antenna on the metal ledge just inboard of
where the poptop canvas attaches ... to the left (driver's side) of the
poptop latch.  That puts it inside the van rather than having to run the
wire outside and under the luggage rack or some such.  With the top
latched, the canvas covers the antenna but both the canvas and the
fiberglass top are transparent to it.  I never lost signal (except in a
tunnel, which was expected).  I am really happy with this location and
it allowed me to fill the luggage rack with stuff (5,000 BTU A/C for
camping, side tent, and tent poles).

Mike
Houlton, Maine