The wet mount in the hull like DS's is a good place to start. I tried beaming through the hull, but eventfully went a little further..
You can read about how I did it here:
http://www.bigwatersedge.com/bwevb/s...ead.php?t=4454
Not for everyone but far superior when it comes to performance.
As to batteries I run two... I'm running a 12v 10ah NIMH battery for electronics, it will power my Garmin 398 all day 12 hours plus with power to spare, and weighs less than a 7.5ah lead acid. It's supposed to take over a 1000 charges. Shows no signs of wearing out after two seasons.
For the bait tanks I'm using a standard lead acid 6v 10ah and it powers the tank all day no problem at a better (lower) flow rate then a 12v. It's definitely the way to go...
Jim