I would say let the female grow to around 10"+ (disk-wise) before attempting.
Otherwise she might get severely injured by the mature male ray in attempt the breed with her.
i would agree but i`d go larger as i`ve had an inch smaller males really damage females but it depends on how aggressive and persistent he is and if the male is mature he will tend to try a fair few times with female that isn`t ready!
nothing wrong with housing them together. the male may try to mate with her, if it gets too rough then I would separate them. there is no proven way or disk size to tell when a female is ready. she is ready when he is preggo.
It would be a gamble. I had a 8.5" mature male motoro pester and bite a 11.5" female motoro. The only time it was a problem was when they were breeding.
Usually the best breeding pairs are smaller males matched to larger females.
But like was posted, they should be able to live together just fine. Just keep an eye on them.
