Hey guys, totally new to owning a boat but ill be getting a mobius lsv later this month with 750s in the back and they usually fill an 800 and put it on top of the cushions up front. What's the best option for under the cushions up front? And can I have it filled with the belly sac pump? I see there is a 650 by straight line on wakemakers but it still say fill with a movable pump