>     I could extract it and send it back to him; it's his problem, but it is
> nice honey and we'd like to buy it.  OTOH we don't want to blow up our
> drums and wind up with worthless honey either.
 
If he has a buyer, he can send it for blending immediately and that is the
easiest solution.  I'd measure the moisture so that the expected time to
fermentation is known.  At 17.5% there is no problem.  At 18-19, several
months is likely safe.  Over that, it can go (very) fast,depending on
temperature and how clean the handling and containers happen to be.
 
If you pasteurize it (not hard to do - use the same times and
temperatures as for milk), it will keep 'forever', and can be blended when
some dry honey is available - or sold for blending when convenient.
 
>     Could I pull much moisture out of it if I warm it to, say 130, and pump
> it across a flat sloping pan, with a fan blowing over it.  Or would I be
> wasting my efforts.
 
This can work, but is slow, messy, and removes the aromatic scents from
the honey.
 
Stacking the supers in a warm room works well, but is slow and it is hard
to get low enough relative humidity in the summer in your area, I would
think.
 
I'd just extract the honey, measure the moisture (visual checks can
fool you, place the barrels (so they are pasteurized too) in a warm room
at 120 degrees F for a day or two (check the actual required time & temp -
I'm guessing here) and seal them -- and quit worrying.
 
Allen