Hi, just need a little advice.  I want to install a small 3 way refrigerator in my  trailer which is just a shell at this time. I want to mount a single battery and a single propane tank to the trailer,  I can get a propane bottle ring at Camper World, but I don't have a battery box yet.  Do I the  battery box or can I get by with the shelf type?  Does the battery mount and propane ring have to be aluminum as they will be mounted on an aluminum trailer or is steel fine?  I will need to take this to my local welder, are these items to be bolted on or welded on?  Many thanks Joan

Here ya go, and I mount the LP tanks right above these.

http://www.jazzsales.com/index.php?route=product/product&path=48&product_id=944

They can be bolted on.