The foam has been poured in along side to the underside of the tank. The risors pulled out as anticipated, leaving nice clean holes. The side rails for the tank bay floor will need to be installed in the gap currently occupied by the risors. I had set a depth on a sawzall to bring the foam down to the proper level. I then applied a coat of resin on top of the foam having cut thru the skin of the new foam. At each end of the tank, I applied an appropriate bead of polyeurathane caulk to seal the narrow gaps between the tank and the forward and aft bulkhead. Now any water that should get into the tank bay, thru the filler/sending unit access cutout will simply run off the top of the tank, down the sides and out thru the risor holes, down to the laterals and out thru the centerline pathway and into the bilge.