Steplift20,  
 
My 78' has one large access panel in the floor, roughly 2 x 5 ft.  I placed the batteries under this hatch, forward of the gas tank on a piece of plywood which I coated with resin.  I ended up using 5200 to secure the plywood.  They are about even with the helm, pretty much mid-ship from a fore and aft prospective.  I placed the batteries to the port side to off-set the weight of my 10 hp kicker which is on the starboard side of the transom.  She goes in the water this weekend.  I will follow-up and let you know how she sits in the water.  Previously my splash well drains were 2" under water...not so good. 
 
Hopefully that makes sense.  I need to figure out how to add images.
		 
		
		
		
		
		
		
		
		
	
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