I hope this helps some : I was told that the miles which comes from a Plat account will have top priority ( besides the fare classes, time of purchase, etc. ).
And when you look at the seat map, CO blocks like 12 seats ( whole 1st row in the BF cabin on the 772s, and whole 1st row in the 2nd BF cabin ). I did not pay much attention to the 764s or 762s.
If the WL does not clear...they will give you back the co-pay and reinstate your miles. What do you have to loose ?