I have a premium snowflake that is paired with a Naked.
I intentionally wanted my Snowflakes to pair up with each other, and not the opposites.
Should be fine until they become true pairs, and start breeding.
By that time, you should only have 1 pair in the tank at most.
not likely to pair, also the percula may start picking on the ocellaris as they grow. For the most part perculas are more aggressive. Although it is not unheard of for a ocellaris percula hybrid to occur just not as common as percula x percula or ocellaris x ocellaris.
Why do you say they are unlikely to pair? Perc x ocellaris pairs are quite common. I have a snowonyx (which is a perc/ocellaris hybrid) paired up with an onyx and there is no problem. With all clowns there is a chance that the female won't except the male you just have to watch and make sure that the female isn't too aggressive. If you get them both before they've picked a sex you should be fine.