parking up hill sounds good to keep spills to a min, but it sucks stuff backwards out of the prefilter back into the fuel line into your tank, just to get caught back in the prefilter again...
counter productive. if you remove the line from the tank side of the filter, and plug it off, NOTHING goes back into the tank, and Nothing spills! then just dump the dirty fuel into the appropriate container and put the new one back on. prime and go...
John