airbus757, you are presuming that VMCG is calculated for contaminated runways. Certainly this isnt the case for FAR's, we only have 1 set of values for VMCG as determined in FAR25.
Alex, looking at the presentation that i mentioned, it shows the same trend for B737-500 aircraft, willing to send you the presentation if you let me know your email.
Cheers
Mutt