Oh b***er! Sorry timstza, I misled you. I meant increase V1 to be equal to VMCG. I was thinking about VMBE, its the heat.

DC 92 32/ 33 RC
 

I have just found same old material regarding this topic.
DC 9 AFM supplied charts to calculate " WEIGHT FOR MINIMUN RUNWAY LENGHT AND SPEED DETERMINATION". Depending on DA conditions it was a minimun ATOW for a balance TO.
When OAT or PA decrease, Vmcg increases, and therfore the minimun TOW is higher to comply with V1/Vmcg restictions.