Unfortunately, distortion and reflection

The Extender would be a welcome help to me as wearing glasses. Unfortunately, it turned out the same in the assembly that this is too high and the eye sensor permanently occupied with the EOS 650D, therefore I need to putter a little, here the decrease of a few millimeters and it worked enough again.

Very unfortunate however, is the enormous change in imaging performance, so the image is recorded extremely barreled. In addition, nothing is non-reflective, which makes it impossible as glasses in the sun photography, but this works wonderfully in return without extension.