plan on doing a battery location on your rig and dont feel like using an expensive metal or cheap plastic battery box? well, take a trip to your local militray surplus store and pick up a "fat 50 " ammo can. mine cost about 10bucks and holds a yellow top optima perfectly. its does cut the use of the side terminals but the battery also comes with top terminals so thats not really a problem. you will need to modify the box to work properly and safetly as a battery box (ventilation, hold down etc) but for 10 bucks or so its a good start.

http://i37.photobucket.com/albums/e74/85burbanator/MultimedMA17088703-0001.jpg

http://i37.photobucket.com/albums/e74/85burbanator/file000MA17088703-0002.jpg

got the battery box about 98% complete. just have to run the cables and drill the holes then it will be done but that wont be for a while. i used 1/4" threaded rod with a 1/4" nut welded to one end and a 1/4" fender washer behind that underneith the flat bed. i then use four 3/8's bolts on the four corners with 3/8"'s nuts,washers and 5/16"'s fender washers under the flat bed. here are the photos

http://i37.photobucket.com/albums/e74/85burbanator/MultimedMA17090790-0003.jpg

http://i37.photobucket.com/albums/e74/85burbanator/MultimedMA17090794-0001.jpg
thats another 1/4" washer and nut to keep the all thread from falling through when tinkering with the battery.

http://i37.photobucket.com/albums/e74/85burbanator/MultimedMA17090786-0004.jpg

under the flat bed
http://i37.photobucket.com/albums/e74/85burbanator/file000MA17090794-0002.jpg

Great idea. I might just do that.

If you need a box for dual batteries, a "rocket box" works great for 2 Optimas (or about any other standard size battery) side-by-side. Sorry no pics, but someone posted up on this a couple years ago here on Pirate, you can search if you're interested in learning more.