That's probably not going to make HIS primary terribly happy. Part of being polyamorous is considering the feelings, wants, and needs of the other people involved in the relationship. I'm sure you do want a lot of time with him but he is already in a relationship and the other participant(s) may not be as enthusiastic as you.
I would take some time and think if you actually want a poly relationship or if you just want a relationship with him in particular.
I personally follow a sort of "personal anarchy" concept; I dont have primaries or secondaries, I have people that I love and care for and that's that. I feel uncomfortable putting people into tiers based on when they came into my life.
I am as direct as a T-Rex with 'roid rage and about as subtle. It isn't intended to cause upset, I just prefer to talk plain. There are plenty of other people here who do the nice, polite thing much better than I can. I'm what you'd call a "problem dinner guest."