The only downside is that the CAP fleet is only 172s/182s, so a CAPF5 doesn't help you rent anything else.
There's a reason a CAP F5 works as an Open Airplane UPC. They modeled the UPC on the CAP stan/eval program! It used to just be a FAQ that said "email us your Form 5," but it's much more sophisticated now: http://cap.openairplane.com/The only downside is that the CAP fleet is only 172s/182s, so a CAPF5 doesn't help you rent anything else.