It's alright, even if you post like the first, or first two chapters this month, and keep it going. Or you can post "Part 1" on June and "Part2" in July, as long as you post something and you mean to finish it one day. It's the first month, so the most impostant thing is to get this thing started, even if it's just with 3 or 4 participants at first. :).
I remember a few years ago I was in a french forum and at first no one wrote anything, then like one or two users, and after like six months there were like six or seven regular users posting new fics every month or so, it became quite dynamic.
