Last question and I'll leave you alone:
Where do I find sheets of neoprene as I was thinking of using engine
manifold gasket material.

I cut 8" square access ports to be sealed with 12" sheets of Neoprene,
formagasket, aluminum sheets, and 8x32 screws.
Step1: Drill bolt holes in the 1ft square aluminum port covers. at
least 4 to a side equally spaced.
Step2: Center the port cover over the cutout, and center punch thru the
bolt holes for the tap drill. Mark a corner for reference, in case the
holes are not uniform.
Step3: Tapdrill, and tap. Note tapping aluminum sucks because it is so
soft the tap plugs up. BACKUP several times, and clean tap.
Step3: Clean all the shavings with a vacuum. (I am assuming you have a
clean dry tank here) Don't want them to look for your filter.
Step4: Lay the port cover over the neoprene, and mark for punching
holes. and punch.
Step5: Spread the formagasket around the port, 2" or more wide.
Step6: Lay neoprene over cutout, spread a 1/4" bead around each bolt
hole, and lay on the port cover.
Step6: Tighten all screws.
OOPS i forgot. The start of this was the fuel guage sender. You get the
idea. I would cut a hole in the port cover for it, and drill and tap
mounting holes. Of course do this before messing with formagasket.
Hope this helps.
http://s90.photobucket.com/albums/k274/densnet/
Den 48yf EAGLE