Introducing Ferrets to Cats

I have a 5 year old ferret and a 8 month old ferret. My 5 year old was a rescue, and had been around cats, (honestly I can't keep him away from the cats.) 

My 8 month old has been free roam since 2 months old, and trouble is now, he does not like cages or even closeddoors, he will dig at my carpets. 

But now, my best friend moved in and she has two cats. They had been raised around a Boxer. So its on day 4 now. and its getting old locking them up in rooms while the other is out because they all dig at the doors. I'll have one ferret out for a few mins to smell and so far the cats, slightly skiddish arent really bothered by them. The 8 month old gives the bigger one Tappy a ear licking. But its the smaller cat and Fenrir I worry about. Alex is the cats name, he walks away but Fenrir just follows him. then today, Fenrir thought it would be a good idea to jump on top of Alex and play like he normally does with Mjolnir the older ferret.  I grabbed Fenrir mid jump and put him in my room. I'm afraid jumping on top of the cat will just scare him and attack rather than going along and playing with him. 

Do any of you have any suggestions? 

I had 3 cats and ferrets before, and there was never much of an issue.  If they're not going to get along, it would be better, IMO, to lock up the cat when Fenrir is out.  Cats won't shred your carpets.  But I've never heard of a cat actually hurting a ferret.  Our last cat was a rescue at 8 weeks old.  He was raised with ferrets but when he got to 9-10 months old he would scruff and drag a couple of my male ferrets like he was a momma cat.  It was weird.  And scary.  We're all about ferrets now so we re-homed the cat so as not to have any accidents.

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