I made a simple tray out of G10 that matched the angle of the floor and center stringer.
I then mounted all of the pumps and switches to this. It is held in place by a 1/4" fastner and a wing nut thru the stringer, so that if I ever have a problem with a pump, I can undo one bolt and remove the whole tray to service them.
Here it is seen thru the aft hatch.
It is only 1/8" thick as well, and you can tap into the G10 to mount the pumps.