installing 2 6 volt batteries

[2014 laredo 299bh]

just bought a 2014 laredo 299bh, was looking for some ideas on how to upgrade to 2 6 volt batteries. New style with fiberglass front end and countersunk 30 lb propane bottles.
Looks like i am going to need to fabricate something as there is only room for one battery up front, and need room to get propane tanks out.
Looking at for some creative ideas location.

THanks