RIchard,
Are you sure the leak is from the interface between the adapter sections
and not from the adapter-to-engine connection? But, since it hasn't been
all that long since you installed the engine, that gasket should still be
good.

Aside from the obvious care to clean the seating surfaces good, I'd be
inclined to use the gasket from a new filter rather than a used one. And I
wouldn't be afraid to TIGHTEN that big ol' nut (from X-7525: Oil Filter
Extension Fitting ....55 ft-lb -- I THINK that's the one we're talking
about.)
Ken H.