Double-wall Canopy mod to eliminate frost

Two, possibly three years ago, I read an article in one of the gliding mags
detailing the attachment of a plexi or lexan sheet to the inside of a
canopy, creating an air space which would be warmed by solar radiation thus
preventing frost during cold-weather high-altitude flights. Trouble is, I
can't remember the magazine in which this article appeared, nor the
particular type glider. Does anyone remember this story? If anyone has a
copy of it, could it possibly be scanned and passed along to me?
Thanks in advance,
Chris