You might also try a crate if you're worried about one of them getting hurt. After I caught my Mowgli, he spent his first 2 weeks with me caged. Once he was given a clean bill of health, I started letting Zelda into the room Mowgli was caged in, and would just sit by the cage giving her attention and assuring her that she was still my princess. Then when Mowgli was comfortable enough with me that he wouldn't hiss and run and hide, Zelda was willing to tolerate him and eventually mother him.

If you don't want to invest in a cage, you could put Tiki in the carrier and set that out where Meko can check things out for himself at his leisure. And while you've got it set up so they really can't get at each other, it'd be a good time for a wet food treat so they can associate being around each other with good things happening.

If you're worried about one kitty in particular being an instigator, you might want to try the harness and leash approach when they're in the same room, so you can at least control the movements of the trouble-maker.

And then there's always Rescue Remedy to relieve stress (for you or the kitties).