If there is movement of the boards, either the floorboard grip is not correct, or the tubeset is underinflated.
Floorboard grip is dictated by the distance between the transom and the bow joint. If you measure the tube fully inflated, then measure the floorboards outside the boat, the floorboards should be about 15mm longer than the boat inside measurement. If it is equal to, or shorter than, likely, one of the joints has stretched or it is beginning to unglue and lose tension.
If it is underinflation, simply top the boat off to the recommend 240 millibar. This must be done after the boat has sat in the water, and the cool water has cooled the air charge inside the tubes.
Gluing geek since 2007