Oh boy, you're making me nervous. I only applied to 4 DO schools. I just finished applying this week. Makes me think I should add some more. I have a 3.65/35.
I applied to way more than I should have. With your stats, 6-8 would be ideal, depending on your ECs.
Yes that's an arbitrary number I just made up.
I applied to 13 schools, got invites from 10, MSU doesn't do IIs, and I didn't get an II from PCOM PA or NYCOM. I was accepted to every school I interviewed at and withdrew my application after being accepted to my top choice.
Certain schools (MSU, NYCOM, and PCOM in particular) tend to have their pick of decent students, so they look heavily at ECs. My ECs were strong (>10,000 hours as a respiratory therapist, 1,000 hours as an ED tech), but my volunteering and research was weak, and I think that's what killed me.
If your 4 schools are not MSUCOM, NYCOM, PCOM, or any of the very state-specific schools, you'll probably receive an II if your PS is decent. Statistically, 50% of people interviewed get accepted at most schools, so if you get 2 IIs, you're probably set.