Welcome to PT. I am sure you will like it here, and there is tons of great advice. I don't know how recently you rescued Slyvester (sounds like a tuxedo cat to me...and we sure love our tuxes!). But, time is usually the remedy. Attrack the kitty to you, or into the room you are using with toys, treats, etc. Make it a positive experience to come to you...maybe Sly wasn't very socialized in his last home???

As to his less than agile ways...some cats are just Klutzes! I wonder what the deformity is? Maybe it is a partial paralysis? Affecting his eyesight? My dad has a cat that is the biggest klutz in the world.. it is kinda funny. I wouldn't worry about that, except to investigate the deformity issue. I would also look in the Cat General thred for the pet proofing thred..lots of good ideas in how to pet proof your home.

As to Kona and Sly hitting it off...maybe they never will. But, they probably just need more time. Others will chime in with their experiences in mixing cats...I would again try the 'forced' interaction...playing near both of them where they want to interact with you enough that they might interact with each other by accident.

Good luck, welcome again, and keep us posted!