Gliders are pretty resilient in my experience. Cut their nails gets them
mad, but as soon as it is over, they are fine.
have a grabby glider in pouch that is really bad, he doesn't bite, once he
calms down I can pet him fine.
So I'm thinking this first bad meeting might not be a problem.
I would do the standard stuff before intro. cages 8 inches apart, swap
pouch every 2-3 days (I think this is important, keep the new scent fresh,
get them really used to it in their life)
I used 2 pouches per cage, and only swapped one, when I noticed both sleeping
in the scented pouch, then after 3-4 weeks, my wife did the intros of 4 glider
and one glider, they all did great.
I think once they are used to that new scent, then when they finally meet,
it won't be invading strangers (intro should be done in a scent free area, we use
the bathtub) but a friendly scent. Also once all are together in bathtub we
give the cage a good cleaning, so they can all scent it up together.
this has worked for my wife about 8 times with many combinations of
gliders groups. We had one failure going 8 gliders and adding 3 new gliders, one
of the 3 was rejected for 3 nights, kept getting chased to corner of large cage, so she was removed.