[Rav Wosner] answers that technically this is permitted since reading through plastic or glass is considered reading the actual scroll. However, he says that he does not feel comfortable giving his stamp to this new innovation. He suggests solving the problem in the traditional way, which is for someone with a Chumash to whisper into the ear of the Baal Korei and the Baal Korei read from the Sefer Torah.
So when a gadol/rav/poseiq says not to do that which is "technically permitted" is this:
- Da'at Torah?
- 1=2 anyway ;-)
- Making up new Halachah?