Does anybody know if there are extra long screws for chinrests available somewhere? The longest ones I've heard of are 50 mm but I need 55.
A luthier could probably modify it for you if you can't buy one to fit. Actually, all you probably need is longer barrel sections and not the screws in the wood.
Yes, but I have no idea where to find such things...
Fastenal Corp. may have such hardward available and they are in most larger populated areas. I have had great success finding difficult hard to find hardware for a multitude of different musical instruments there.