Have you already got the Halo? From the specs, it seems like it's just a very pricey 9 dBi antenna and a MiFi device. If you've already tried it, does it live up to the claims in the brochure?
You can drill a hole through the rear cap of your Bighorn. Measure inside and out 4 or 5 times to ensure you know where the bit will come through on the interior. The roof material is draped over the back before the cap is installed, so you may be going through the rubber membrane, which will twist a little around the drill bit. A
clamshell wire cover over the entry point will protect from water intrusion.