I have a 1995 2520DVSC with a single F250. In my opinion, the tank should be moved aft. My deck bairly drains at rest, especially with less then 1/2 a tank of gas. Twins would alter the equation somewhat.
Also, I'm pretty sure my tank extends nearly all the way up to the bulkhead where you step down into the pilot house. If they moved it forward, I would think the pilot house would be impacted. Is this the case ?
On my boat, the area forward of the stern hatch is wide open for several feet, and the bilge is very deep at that point. Bottom line, there is oodles of room to add something here. I'm reluctant to do anything because of the safety aspects of a sealed deck and I hate having to clean fishwells whenever I'm on boats that have them.