Hi Gil,

I did a few quick measurements of my Losmandy G11 mount bottom, and saw
the dimension Drawing of the AP900 Pier Adapter Plate, and see it is easy to
make a "reducing" adapter so that the top of this 2" or 3" tall ring has the
shape and 6 small screw holes - as though this were the top of any AP tripod -
to accept the AP900, then is cut inward, to the shape and dimensions of the
Losmandy head base at the bottom.

Here is a direct link to the AP "Pier Adapter" dimensions document, at
their Tech Support page, under the AP900 list of PDF documents (consider this
the same as the bottom of your AP900, which drops into an AP tripod pipe):

900 Mount Base (Pier Adapter) Dimensions (05-17-00)

The bottom of this plate is the same as the bottom of the AP900 Standard
or Rotating Pier Adapter, which you would be already using on that mount. Have
your machinist make the top 1/2 inch or so it accepts this base. The bottom
of the reducing adapter is just a narrower cylinder with 3 holes to screw in
the Losmandy G11 screws/knobs.
It's like a "gender changer" - female AP900 at the top (like the pipe), and
G11 male at the bottom.

After that, you can treat the AP900 mount as though it were a G11 mount -
for your Losmandy tripod - or with MA option, if you like using the Meade
tripod legs (or any other heavy photographic tripod) with a Losmandy MA bolted
on top of it.
This "reducing adapter" opens up both Losmandy and Meade tripods
compatibility for the AP900.

I assume you have purchased the optional Losmandy knobs - they are so
convenient. You might buy an extra set for your G11 adapter. They make it
soooo easy to just drop the heavy mount straight into it's pier, knobs and
all.
My plan is to make this "coupler as short as possible", so it stays
attached to the AP900 mount (pier adapter) permanently, just like the AP900
actually had a Losmandy G11 mount base. That way, I can simply drop the AP900
directly into my G11 tripod, or into my Losmandy Meade Pier Adapter (MA) -
same thing.

The down side, is that the AP900 mount still needs to fit into your
travelling case - you may have to remove a bit of foam since the Losmandy
adapter remains screwed to the bottom of the AP mount with those 6 permanent
screws. Since I haven't received my AP900 yet, I can still search for a
suitable case for it to fit this modified bottom shape.

NOTE:
If you buy a SCOPEGUARD case for the AP900, they use their own standard AP900
shaped pre-cut foam insert, which won't be cut for that 2 or 3 inch adapter -
and the case might even then be slightly too small (don't know). I plan on
using a suitable Pelican case, and remove the foam cubes myself to fit the end
result.

Since at this point you are just a "possible 900GTO owner" as you say,
then we are in the same boat. I won't start machining until it arrives so the
result can be test fitted to both parts.

Meanwhile, show your friend your current G11 tripod, and give him the
AP900 pier adapter plate dimension diagram, in preparation. It's so simple, AP
should have done this a long time ago, since a lot of AP mount owners are
current or former G11 owners as well. Makes VERY good marketing sense. Heck,
it may even help Scott sell more of HIS tripods, for those like me who don't
like the AP tripods. Then again ... maybe AP doesn't want to encourage
customers buying Losmandy's tripods, and Losmandy doesn't want people buying
AP's mounts instead of his own G11 etc :-)

I'll work on my own sketch for this soon, but I think there is enough data
for your friend's advice already.

Good luck,
Joe