[Antennas] Base for Comet HP32?

[doc]

Just acquired a new Comet HP32 2/440 antenna.
http://www.visradio.com/dwg/ncg/hp-32.gif

It is an extremely rugged dual band with gain but I failed to 
note that it didn't ship with a base.

What recommendations do y'all have in the way of mag 
mounts -- I am guessing that a heavy duty mag mount in 
the center of my Astro van roof will provide better 
performance than an edge mount -- yes?

Thanks! & 73, doc KD4E