Yes this is correct. I have done this on two of my trips - once when I had more than 2 people in my traveling party, and once where my preferred itinerary was more than the allowance. Passport Travel booked all of the tickets, my Seven Stars/Diamond flight credits took care of the two tickets, and I gave Passport Travel my credit card via my host for the other tickets/overage. I didn't want to use RCs at a 2:1.