I am rebuilding a broken Nikon FM and upon opening the top cover I found decaying foam material on both sides of viewfinder. I am planning to cut new material but there are two small lens on left and right side of VF and I'm concern if I will block them from light path. Anybody can describe or post picture how the original foam looks?

Here's the picture of the FM viewfinder area, you can see the decaying foam on left and right of VF just under the small lenses (they're almost disappear).

PS. Oh and I hope anyone interested or having info in rebuilding Nikon FM can post on this thread for future reference. I hope you don't mind.