I think u are right. If u have to waive two (Prince and Nate) it sounds like a 3 for 1. The only way it works in the trade machine is 3 expirings for rivers.
Get Hedu, udoh, and CDR. Waive Hedu.
Leaves us with 14. CDR and Udoh are the odd men out but if Bass and Thornton leave, they could actually end up being the 9th and 10th players in the rotation, replacing Bass and Thornton.