I'm not sure how warm the mats might get, but I've found too much heat tends to accelerate the fermentation process, and affect the end product.
We keep our house around 65 degrees also.
Most lactic acid bacteria work best at temperatures of 64 to 72ºf.
The Leuconostoc bacteria, which begin the fermentation, have an optimum of 64 to 72ºf. Temperatures above 72ºf, favour the lactobacillus bacteria.
But,in general, a temperature of about 72 degrees will be sufficient to ensure a lactic-acid fermentation.
I almost always have something fermenting, and I just put my jars on top of the refrigerator inside black cotton sock.
The sock blocks the light,that contributes to discoloration while also supplying a little insulation.
I keep a thermometer close by to monitor the temp., which holds pretty steady at 73 or 74 degrees.
Another thing I do sometimes when its exceptionally cold, is put them on top of my clothes dryer during a cycle, to bump up the heat a little, then its back into a sock and on top of the fridge.