I'm rebuilding an old BSA Improved Model D rifle with a 17" barrel which I guess could make it a light pattern and I notice that the leather piston washer I've just removed, which I doubt is original, is in two pieces, an inner harder disk and the outer. It's in very good condition but the replacement I got from Knibbs does not have the harder inner circular disk of leather as does the one I've removed. Can anyone tell me which type is correct ? Also, the new metal cup washer that came with the leather seal, that the fixing screw goes through, does not appear to have a deep enough relief or dish in it and as a result the screw head is quite a bit proud of the assembled washer set up. My concern is that from it's appearance if fired the screw head will slam into the front end of the cylinder. This can't be correct can it ?