8mm hotbed spring washers with insulation support

I liked the spring washers from http://www.thingiverse.com/thing:1895223 and I had a cork sheet for insulation under my hot bed. The other solutions spanned the bed, and seemed like overkill. Four of these can replace the top washers on the springs, and hold up a 4mm cork sheet under the bed for insulation. Overall, this cuts my heat-up time in half with virtually no effort.