1988 Mastercraft Tristar 190 question

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I have a 1988 Mastercraft Tristar 190. The previous owner of the boat made some modifications including converting the rear seats into a sun deck and installing a fat sac under the sun deck. The wake this boat throws is awesome for boarding and surfing but the space that is lost to the fat sac/sun deck is ALOT considering the interior room of this boat is already limited. So, what I would like to do is figure out a way to 'bury' the fat sac under the rear seat and put the rear seat back as it originally was; basically I want to eliminate the sun deck and put the fat sac under the rear seat. If there is a clever way to make the rear seat convert into a sun deck that would be even cooler! Has anyone ever done this? I did notice the floor area where the rear seat is supposed to sit is elevated from the rest of the boat floor, but I am not sure what is under this elevated area. Can I bury the fat sac under the elevated floor area? I have added some pics of the boat and will get more of the current sun deck configuration soon. Any help is greatly appreciated!