My feline problem...

Permit me to vent here.  I'm getting near my wit's end, and not sure what the best solution is.

I've had a cat, Smokey, for almost a dozen years.  My brother and I got her from the Cleveland APL, and she's been a great pet.  Generally quiet, occasionally snippy, but always part of the house.

When I first met Katie, I warned her that Smokey was shy and generally hid from people.  An hour later, Smokey was purring on Katie's lap.  I took that as a good sign.

Smokey's getting up in years.  She doesn't run much and climbs the stairs slowly, but the vet confirms she's in good health.

The problem is Pippin.

A month ago, some friends of ours had a problem- they had two cats, but after moving and having a baby, one of the cats (Pippin) was reacting badly, spaying the house.  They needed to either find Pippin a new home or put him down.  And I volunteered to bring Pippin over and see if we could take him in, hoping that without a baby, Pippin would calm down.

To be honest, it's worked out better than I should have hoped.  Pippin is a huge adult cat, but extremely friendly.  Unlike Smokey, who likes to hide, Pippin is always walking around and rubbing against people.  He likes to be petted, and there has been no spaying problem with him at all.

But Smokey is absolutely terrified of him.

In retrospect, I should have realized it.  Both are adult cats, but Pippin is twice her size.  Both Pippin and Smokey are fixed and have their front paws declawed.  I was told that cats take a few weeks to get used to each other, but we're on three weeks now.  Smokey is always either hiding from Pippin or hissing and attempting to strike Pippin.  Twice we've heard a 'yelp' and seen Smokey run and hide under the bed, but weren't able to see what happened exactly.  And now I'm worried Pippin is starting to use Smokey's litter box instead of his own.

I'm at my wit's end here.  I'm open to suggestions here on getting the cats to get along.  We've already bought a diffuser to try and calm Smokey down (Pippin always seems calm), but every day it seems like a case of "one step forward, two steps back" with the cats reacting to each other.  For my own sanity's sake, I can't have the cats being this neurotic around each other.

I've talked to Scott, and taking Pippin to the APL is a possibility.  Since we know Pippin doesn't spay, he can be adopted.  But I really hate the idea of taking an adult cat to the APL- it's too easy for him not to be adopted at his age.

I'm asking my facebook friends if anyone would be interested in adopting Pippin.  He's a fantastic cat, and can make a wonderful pet.  I don't want to get rid of him, and if I do I want to make sure he's going to a good home. 

Volunteers and suggestions welcomed.