Flattening warped lp's with Seal dry mount press

I've been meaning for some time to try a test flattening warped lp's with my Seal dry mount press. A recent purchase of two warped White Stripes lp's & the recent tread that Albert Porter & others have had about the topic prompted me to start an experiment. For the first test, I placed a warped 70's Columbia pressing in the press between a 1/2" tempered glass plate and a 1/4" thick acrylic plastic plate, setting the thermostat at 165F. I did not pull the press handle to clamp, I just let the weight of the heating platten do the work as things softened. After an hour, the vinyl was quite flat and I let it cool down for the afternoon. While it looked excellent at first glance, there are problems. There is radial runout now, about 1/8" or so. Even worse, there are small hills and valleys in the vinyl surface that set my Grado Sonata wiggling and shaking. Evidently, the heating, pressing, and cooling process is creating stresses that leave things less than perfectly circular and flat. Next, I'll experiment with less heat and longer thermal heating and cooling cycles to see if stresses can be relieved to achieve better results. At this point though, I don't think I'd run out and buy a dry mount press hoping this to be an easy fix. It's going to take some experimentation to see if this will work. I'll post results as I work through the variables.