Thank you both for the replies. I should have been clearer in the original post. The 4 man crew legs will be operated under 121.523. As for the two man legs, it will be under 20 hours of duty time. The only limitation for that leg seems to be flight time under 8 hours.

If I am reading 121.525 correctly, it wouldn't apply since I am only interuppted once going from the 2 man to go back to 4 man.

Thanks again for all the help!