Considering the hatch for the battery access on the B+ is about 5" high and 10" wide the above will not work. I talked to Charger Enterprises in Elkhart, IN about the problem in 2012 before our Alaska trip. The unit design did not lend it's self to the above type of alteration. They modified the battery tray to hold two batteries and through bolts under the sofa with weight distribution plates to carry the weight. At the same time I made the change to AGM batteries to solve the watering problem through the small access door.
On edit: typo date