Has anybody had experience with these heated soles in a glider: http://gerbing.com/Products/insoles.php ? would it be better to get sock?

Some of these types of products have horrible reviews but these have good reviews on a retailer's website.

Most of the threads on heated socks are old and are about wave flying. My issue is that it’s often over 105 degrees F on the ground but after a few hours above 14k my feet get painfully cold and would like something that I can turn on later in the flight.

I’m thinking of powering these off a dedicated sealed lead acid battery as I think the newer batteries are risky: http://www.youtube.com/watch?v=mlZggVrF9VI

Thanks,
Jim