Noticed two issues about breaking into the berth floor: checking for moisture and creating more storage. Now that the Marinault has surfaced with its side tanks, I'm more apt to put my energy and costs into gettng custom tanks fitted beneath the gunwales on both sides (haven't found how to attach them yet) and getting those blasted batteries down on the sole where they belong plus creating mucho new space for more storage after jerking those gas tanks under the well and cleaning up all the gunk that manages to get behind them.
A thought about the installing of hatches below the mattress. Which is more work, lifting the stiff mattress up high enough to lift the hatch cover up and reaching down to grab stuff, or....moving the porta potti forward to access a hatch which is vertically located on the end? Seems that cutting into that area would hurt nothing, and one could scoop out a big area ahead, enough to shove stuff into. Storage and checking for moisture in an area that is a whole lot more accessible than a hatch below the mattress - that makes more sense to me. But then I lost my flexibility a long time ago. Food for thought folks. If you already did the under the mattress contortionist thing already. OK. You can still do the end entrance and I'll wager which system you will use 99% of the time.
John