Good morning!
Alright, I'll speak to this a bit. I am not an expert in this, and if another member reads my post and corrects me it won't bother me a bit! Since there's been so few replies maybe my answer will get the ball rolling. Plus, I know there's lots of members with varied experiences and different perspectives so I'm ok if someone posts something different from what I say because I know we all have a common purpose: to help fellow glider owners.
Anyway (lol I ramble) ...
I have three completely different experiences with over grooming.
The first was my lone glider over groomed her tail. I suspected she was lonely, got her cagemates, and she stopped.
The second was another lone glider who I was trying to integrate into my colony. She also over groomed her tail, and I suspected this time it was the stress from my colony because they were not accepting her. I moved her to a different room, got her a different cagemate, and she stopped over grooming.
The third is my Gimli. He overgrooms above both eyes. To this day. I've tried everything! More toys, less toys. More out of cage, less out of cage. Different diet. Change the cage more frequently. Change it less frequently. Frankly, I think it started when I got Luna (glider in different room) but honestly I'm not sure. In that case...I'm not getting rid of her soooooo...
I've done research on it because I know most people think it means the glider is sick or stressed. But here's the thing. I think he's a happy glider. His cage is huge. He has a solid colony, lots of toys, and a good diet. I'll try one more thing: a humidifier. I'm buying one this week. But I don't think it'll change anything. At this point I think it's just a habit for him. Maybe it started with stress, but I believe now it's just habit.
For your guy...yeah, maybe he's had stress. But now you're helping him: bigger cage, better diet, more toys, better care overall, right? So, maybe he'll stop. I hope he stops! But if he doesn't, then maybe it's just habit.
Having said that, it's always a great idea to get your new glider vet checked as well.
Hopefully that helps!
Cheers!