Well, do I feel like an idiot (but I have redeemd myself at last).   For
years, I have been unhappily dealing with a cheap chrome plastic sink drain
which was bought from an RV supply place.  I tried buying a nice stainless
unit from a plumbing supply place, but could not seem to get it to work.
Both drains would stand up too high from the bottom of the sink and prevent
the sink from draining completely.  If I tried using anything other than the
included thick rubber gasket (which was causing this problem) the sink would
leak badly.

Well, as I was prepping the Syncro for our upcoming trip, I came across the
nice stainless sink strainer unit under my rear seat.  Staring at it and
wondering if I should throw it away it suddenly dawned on me:

"What if I put the gasket *underneath* the sink, and simply butted the drain
into the sink directly..."

Lo and behold, I have fixed my problem.  Doh!   I dropped the strainer into
the sink, and then from *underneath* I fitted the thick rubber gasket, and
then screwed on the P-trap assembly hand-tight.   No caulk or other goop -
just the hardware, and it works perfectly.  Now I even have a strainer to
catch junk which will also stopper the sink.  (It has been holding for over
an hour so far).   I will be a proverbial "happy camper" now!   ;-)

Here is the type of unit I used:
http://www.cornerhardware.com/hardware/iteminfo.html?action=iteminfo&item=03
2888312029&cat_id=594

The package is labeled "JR DUO STRAINER  75-2128"

Brent Christensen
'89 GL Syncro Westy "Klaus"
Santa Barbara, CA