For a commercial operation to tell someone to allow a week makes plenty of
sense. Don't promise a day or two, state "you need a week", and then if he
gets done early the commercial operation is a hero.

No, it means the commercial operation never gets to see him.

Honestly, everything you say makes sense to me too. If you're dealing
with a glider club or a commercial operation of limited resources, it
won't happen. I know a couple of commercial operations that could
accomodate him, but of course they are local to me, thus not in
California. How can they accomodate him? By making sure the schedule
for one training glider is clear for the weekend, the same way a power
school would rent a plane out for a weekend trip, and by making sure
one instructor is available to spend the weekend with him. I once did
something similar for a pilot who wanted to add his commercial glider
and CFIG (he already had power CFI and a foreign private glider ticket)
and it was not a problem - we banged it out in two days of flying. It
meant making arrangements in advance, that's all.

I don't doubt that there are instructors like me in California who only
instruct part time but can clear down one weekend with some advance
notice, nor do I doubt that there are commercial operations that have
the capability to reserve one glider for a weekend, again with some
advance notice. The trick is finding them.

Michael