you might want to be carefull when you screw anything into the decking in your basement floor. reason why is that the holding tanks have a flat top and the are mounted flush to the underdecking. i found this after pulling the belly pans loose from under the trailer.
thanks for the input on tank location, i suspected something like that and used #6 pan head sheet metal screw, that are only 1/2 inch long. they hold very well ... this was after i tried to move the mounts for the dinning area table and found how shallow the flooring is in the slide ... tears up the carpet when the screws are too long.
good luck, gg