Matt>   Yes, I'm using mem-full HCAs.  I could try reflashing the
    Matt> firmware for memfree if that's of interest.

No, probably not.  If I get a chance I'll do the opposite (flash
mem-free -> mem-full, since my HCAs do have memory) and see if it
makes my results stable.
  
    Matt>  I was hoping someone else would do this.  :) I'll start
    Matt> working on it tomorrow if no one else gets to it.

I might get a chance to do it tonight... I'll post if I do.

 - R.