In many trainers, the glass cloth or tape on the center section also helps reduce crushing from rubberbands. (trainers that don't have glassed center sections frequently use thicker sheeting and seem to have an extra rib or two in the center to stop crushing, or so it seems) So, if it's called for, I'd do it.

If you wanted to replace the cloth and save weight, look at some carbon fiber cloth.

I've been doing glass and epoxy jobs on most of my combat planes, and it doesn't add that much weight, and the strength is worth it. I do it in two parts, the bottom first, overlapping around the LE and TE by about 1-2", then the top, overlapping on to hte bottom by the same amount. This doubles the glass at the LE and TE, and really reduces rubber band crush. Not the only way, but works for me.