Usually warping in ABS is caused by very hot ABS from the nozzle of the 3d printer cooling down fast and shrinking. Thus the higher the temperature difference betwee nozzle and bed, the more warping. That's what you learn everywhere.
So I usually crank the heated bed up as hot as I can to keep the temperature difference between top and bottom of the object low and thus hope to reduce warping.
So my bed is usually at 120°C and with problematic prints at 130-135°C.
It seems that PLA melts and expands at these temperatures and thus creates warping of it's own.
I should run the bed at 55-65°C and run a fan as strong as possible.
(During CCCongress I ran a big fan and the warping became much stronger instead of lower.
But then again I had raised the bed temperature to 130°C because the fan would cool the bed.)
Didn't try 55°C yet, will do so in the next print and update this posting with the result.