Hi guys...thanks very much for the endorsement and for the nice words, by the way. Mirror dampers should be open-celled foam. They're principally a sound deadener and secondarily a light seal. In some camera designs the light seal aspect of mirror dampers is a very distant second. Hinge end seals are very important...probably over 90% of camera leaks begin here. Thickness is critical. Too thick and you can get the door out of whack and create more trouble. Compressibility is important, also. Using a craft foam (foamies) is a really bad idea for hinge end seals on cameras such as any of the Olympus OM series, Nikon FM series, Olympus XA first series, Minolta Hi-Matic series, most Konicas, some Canons and scads of other cameras designed to use a hinge end seal of 1mm thickness or less. Craft store foam is stiff and has very high compression set (meaning poor and slow rebound)...to me it is like putting tractor tires on a Ferrari. The long thin slots don't usually leak light, but in some camera designs they can. The other culprit to watch for is film canister window seals. In many cases these are worse than hinge end seals for being the first place to leak light. Please do not try to laminate craft foam up to a thickness that can be used for these seals. It is totally incorrect for canister film window applications and in the worst case will compress the film canister to the point where the back side of your film will be deformed, ruined, scratched when it comes out, hard to advance and next to impossible to rewind. Some cameras using film window canisters also used auto-advance and rewind, and this can be death to a plastic gear train. If you need foam to finish a job or for any application, please contact me. I keep "offcuts" I will send rather than see you use the wrong material. Piracy and fraud committed by another person have caused me to only sell pre-cut kits now. Those instructions I posted for everyone to use have been plagiarized and also sold by this person and others. Oh, one more thing: please don't overlook mechanical troubles. Many light leaks come from missing screws, broken camera bodies, etc. The most confusing case of this I've seen was a cracked/broken take-up shaft collar in a Nikon EM. Yes, it was plastic. How it got broken we can't say but it was able to let light in when light struck the rewind knob at a certain point, and it doesn't take much light to pollute film.
Jon