Quick question: LENGTH of under-seat (dinette) storage, 2619 next to heater.

[rickst29]

My own 2619 is in the garage for winter, and snow "issues" make it difficult to pull out for a measurement.

My curb side dinette seat "storage" is completely filled by the 40-gallon water tank, water pump, and related piping. My question concerns the street side:

A portion next to the entry door is "filled" by the containment box for the cabin's propane heater. But in front of that, there is a storage area.

I need only the free length between the front TM wall and the heater box wall, halfway up. Please ignore short wood pieces at the bottom, used to hold the wood walls of the storage area in place.

Why?

My new 280AH "battery pack" (4 cells) is 14.75 inches long. But I can add add additional cells in groups of 4: each additional set would add 11.375 inches into the 'row' of cells. The total length of 8 cells would be 26.125 inches, I think that would fit. 12 cells would need 37.5 inches, that probably doesn't work. Can someone check that for me? Thanks in Advance