Tinted glider canopies as sold on new gliders are nothing to do with increasing UV protection. They are intended to reduce IR transmission into the cockpit and make it a little cooler. That is why they are at the blue end of the colour spectrum i.e. the opposite of "blue blocker" brown sun spec lenses. Most heating in the cockpit on the ground comes from the greenhouse effect and that is only slightly reduced by tinting but my own subjective impression is that direct sun on to my person feels a little less hot through a blue tinted canopy.