Scott,
I don't think a mounting plate is needed. It LOOKS like there is a bracket which would mount on a mirror or some other "likely protruberance".
Also, look at:
Maximum Performance Marine & RV WiFi Kit EPR 4 watts.
I think that set up would be the nuts for long distance wifi. I use a cell card from att/cingular myself. Great coverage with no limit on minutes for $2 per day.
I have an amp and trucker antenna as well. I've been using it on my E-350 van and am anxious to try it on my MH which I just bought and have not yet picked up. See my recent post in the new members forum.
John Wolfe - N2XBW
AIR 14867
'84 Excella 270