i have put those batts in my front storage compartment. they are to big. the height will cause the post to hit the top. Also the boat will pitch foward it nobody else in the boat. One batt in there is perfect for weight distribution..(i picked up 3 mph) i wound up putting my battries in the large storage compartment and made a rack for the front one to hold plano boxxes. Also if you put them in the front the vapors will put a white sheen of acid on the metal that will eat thru if not maintained, another reason to use the large box, its plastic. i have a 65 at and it will pull my boat . (also a pt17.5)along at almost 4 mph, i unfortanately found out it will do that for over 4 miles into a head wind.
post pics when you are done.
mike