I'm on pins and needles awaiting the exciting conclusion to this
soaring drama. Can't wait to hear how it all turns out.

==============

Here is my idea: I had to do something like this to get some ductwork
through a crawlspace. If you can feed something down into the hole
from the outside, you are a long way towards solving this puzzle. I
would push down some stiff wire like fencing wire or some 0.041
aviation safety wire. You might need to start with light string. It
will be an somewhat easy matter to retrieve the string, then wire,
from inside the fuselage (long stick, etc). Now feed the tubing back
along this stiff wire (wire goes inside the tubing of course).
Champhering the inside lip or streaching it with needlenose (warm the
tubing first) is a great idea to get it started on the tubing. I
definately don't like putting any type of lube on the inside of the
tubing as this could get into your vario. Bad news.

Now, how to force the tubing onto the stem? You need something long,
light weight which won't deform. One inexpensive idea is a suspended
ceiling T shapped main runner. Find them at DIY stores. They are 10
feet long, cheap, and fulfill the other requirements. Attach the
tubing to the end of the T runner. I don't think that tape will do.
I am thinking some type of lasso through a hole at the end of the T
runner so that you can grip the tubing strongly and still be able to
release it.

Now, how to apply upward force 9 feet out? Tricky. I think that you
can get something about 4 feet into the fuselage that could be used as
a fulcrum for a lever for the T runner. A box might do. Be sure to
tie a string to it to retrieve it. A second T runner could be used as
a kind of "hammer" to bang on the bottom of the first runner which may
help.

Good luck. Take deep breaths. Find a friend to help. May the force
be with you.