Any of these "rules of thumb" been taken to your chief pilot and included in your companies SOP? Hmmmm thought not.
Don
No need to take anything to the Chief Pilot, my Boeing QRH Manoeuvres Chapter under RTO's already states:
"Prior to 80kt, the takeoff should be rejected for any of the following"
"Abnormally slow acceleration"
In the absence of Boeing Data to support their statement, I and other crew have put checks in place to gauge whether we consider acceleration is normal.