I recently put 1.25"-2" adapter to a few my eyepieces to convert them from 1.25" to 2". The biggest problem is that the bottom of the 1.25" eyepiece is exactly as the bottom of the adapter so if I put 2" filter then the bottom of the eyepiece will touch the glass of the filter and scratch it.
Has anyone seen some kind of 1.25" spacer or washer, similar to parfocal rings, but thinner. Like 1 - 1.5mm thick. Just want to put it between the eyepiece and the adapter. In the worst case I'll use parfocal rings, but if there is something much thinner I'll rather use it than parfocal rings.