You can have as many alum as you want...
The chapter has to have nametags designating alum as well alum and you can't speak with PNM's other than to greet them. I know our VPR had mentioned something about alum rules changing but I think it had to do with contact, not with how many, I'll let you know
Just a little advice get there early it's a pain to get signed in there.
At one point in time to make things even (while trying out a pilot NPC program to make formal rec. less formal) panhel had only allowed so many women for the first set of parties, but it didn't really help it actually made things worse and here we are back to formal recruitment.
Pitt doesn't have a set skit night or philanthropy night. While recruitment is capped at $700, it is still not anywhere near the "no-frills" NPC resolution, lol.