No, I didn't reinforce under the floor. That thin tabbing from the original floor, which I ground back to be about 2" wide, really provides tremendous strength - after all it was all that Amel relied upon in the original construction. With the new floor just about touching the hull sides, it gets huge purchase on the old "thin" tab and, since the hull slants inward under it, any downward force is really disbursed nicely into the hull sides. Actually, when that had cured, I knew I had a good structure, even before I filleted and tabbed in on the top side of the floor.
So now I've got essentially the the full strength of the original Amel structure, plus yet another identical structure on top of the floor. Jumping up and down on it, albeit just anecdotal evidence, tells me this sucker is REALLY strong (and, I lost my girlish figure long ago!). So that's my story and I'm stickin' to it!
Cheers, Craig Briggs, SN68