From my understanding of Trans fluid, the ideal or recommended temp is around 175-215ish. Under that the fluid is losing viscosity and becomes thick, above those temps you start cooking it. So having super low trans temps isn't ideal to keep your trans happy, the fluid can't lubricate properly if it is closer to pudding than liquid.
Edit: Unless you're changing the trans fluid to match your trans cooler, then you can disregard this post.