Roster decisions - NO RB's impacting flex and waivers

Hey all,

I am in a Yahoo league where you essentially get points from everything from 1/2PPR to first downs to carries. I have Ingram and Kamara for my RB 1 & 2 and roll them out together every week. I also have Jay Ajayi and Ty Montgomery on the bench.

My question is which of the backups for NO should I keep. I have Trey Edmunds and John Williams. I was thinking of dropping one for a waiver pickup for Doctson for a spot start as my Flex options are kind of weak (Sterling Shepard, Larry Fitzgerald at home, or Jay Ajayi). Any thoughts?