Long story short, our little 5.5 year old sugar glider Lila just lost her cagemate Daisy (we called them sisters) due to a cancerous abdominal mass. We had to say goodbye to Daisy, which was the hardest thing I have ever done. She was only 4.5 years old.

Fast forward, about a week after Daisy’s passing we looked into getting Lila a new cagemate so that she wouldn’t be sad being alone while my husband and I are at work. We got a beautiful Cremino and her name is Luna (which means moon). The Breeder told us she was 4 months old (born on August 20). She was an only baby, and I am concerned about her size. She is noticeably larger than Lila. Can gliders be larger when they are an only glider born in the pouch? The mom also kept her for 86 days in the pouch instead of the usual 74. She is a reputable breeder, so I don’t think she lied to us.

We have been working hard for 5 days now getting Luna bonded to us before we completely introduce them face to face. They have been in separate cages and really seem like they are interested in each other. Here is what we’ve done so far:
1. Feed treats to show Luna hands are good
2. Attempt to reach in pouch during the day (she drew blood on my hubby quite a few times but isn’t lunging)
3. Fleece swapping
4. Spending as much time with both of them as humanely possible
5. Talk and interact with Luna at night as much as possible
6. Always try to show Lila the same amount of attention in fear of her getting jealous.
It’s been about 4/5 years since I’ve had to go through the bonding process, so I need some help for sure.

My concerns:
Lila is used to roaming her gliderproof room as she wishes, with Luna’s cage being in there we sometimes are taking her into another room to play in fear of her jumping on Luna’s cage (she still is a bit skiddish). How long should I rep them in separate cages? We have a new “neutral” cage coming in the mail within the next few weeks and also have physical apts with our exotic vet for the both of them Jan 7th, so if they seem like them might get along should I not wait the whole month? Any advice is much appreciated!

there are several sites, including this one that have write ups on introductions.

you want the gliders to be used to the others scent, and except it as friend and
not enemy, so they dont fight during introductions. with just two gliders that
should be easier as they probably both want to be with another glider. but each
glider is different and may take a different amount of time to accept the new
scent. we have done it in two weeks and some in 2 months.

2. Attempt to reach in pouch during the day (she drew blood on my hubby quite a few times but isn’t lunging) at this point I would try to do things that
don't require the glider to bite you in defense of their safety. (or what they
think is their safety.) but if you have to my wife would make a fist so the
glider couldn't get a blood bite easy, also do this at daytime when they are sleeping and less likely to be aggressive. (my recommendation)

a cage that is also cleaned off so most of the scent is gone is also a
"neutral cage", it doesn't have to be a new cage.

you have to make a judgement call, based off of how your glider personality is
and how they react to the new scent. I would swap one pouch and leave one clean one in each cage. I notice the gliders always sleeping in the pouch with the other
gliders scent, so thought it was ok to do introductions. they might have a spat
when first smelling each other, but then settle down and be good, going into a
clean scent free pouch and being together without fighting. if they have a big
fight or two I would stop intro and try again another day.

so if they seem like them might get along should I not wait the whole month?

30 day is a disease quarantine, make sure if one is sick they don't infect the
other glider. after 30 days have a vet check, if all healthy then good to START
scent training.