Directions call for securing fore and aft floorboards semi permanently with wood screws.  I have never liked running screws into the end grain of plywood and I feel this method makes removal of floorboards for cleaning difficult. Instead of wood screws, I installed blocks on the frames into which I installed threaded inserts. This allows the use of 1/4 x 20 x1” round head machine screws.  On the floorboards I used a Forstner bit to recess fender washers. 

This should make removal of floorboards quick and repeatable without long term degradation of the plywood.