I don't know if any of the US PGA events are held on courses that have 27 holes-I know that Hamilton and Oakdale (Canadian Open hosts) each have 27 holes and they usually take a couple of the original nines from the first 2 courses and replace them with ones from the third-and reroute-maybe for TV.
Anyway, I was thinking (

) Aside from the time to build the third course, would it be difficult to do three nines and join the 9's into the three combinations (A-B, B_C, A_C) or would you need to do a full 18 holes for each?
Sage-this is one of the issues at Hamilton.