I'm using an Usher gascolator, which seems to be the shortest one I can find store-bought from ACS. I didn't go with a firewall mount, because the gascolator sump should be the lowest part in the fuel system so as to facilitate catching water when you are draining the tanks. Firewall mounts work on tricycle gear airplanes which are nearly level on the ground, but not well on taildraggers IMHO. To avoid heat from the exhaust tunnel, I ended up with mine immediately aft of the landing gear struts in the deepest part of the fuselage. The bottom portion extends down through the fuselage about 1/2 inch. I made a bottom panel draping some .032 2024-T3 aluminum over the stringers, and made a cutout so as to have access to change/clean the filter (as well as adjust the bottom elevator cable bellcrank) without having to pull seats and floorboards. The gascolator mount also stabilizes the floorboard, which the pitch servo will like.
