I have a trunk mounted alum fuel cell . I would like to change the 2 x -10 an fittings on the sump to 2 x -12 an . Can this be done and not have a leaking problem ? the fittings in the cell now look like they are somehow back nuted to the cell and have a white teflon washer visable from the outside of tank . is it just a matter of buying the new fuel cell -12an fittings and putting them in where the -10 an fittings are ? Thanks .