Converting to dual 6 volt batteries?

[Akegb3]

We may be doing more dry camping than expected so I’ve been researching the use of two 6 volt batteries rather than the current 12 volt or dual 12 volts.

Today I was told by a local RV shop that there’s probably not enough room on the TT tongue, but I’m not convinced that is true.

Has anyone already done this on a 19’ Passport or similar and had some advice or pointers?

Thanks, Ed