Please can someone offer advice on the following:

I am in the process of stripping a BSF S60 model with a scope rail for servicing. The procedure I am concerned about is getting the scope rail off, the rest I am OK, and have my home made compressor with adaptors to remove the spring, I have already serviced my BSF S60 model without scope rail.

Am I correct in the following procedure :

1. Remove the one and only scope rail screw.
2. Tap scope rail back a touch to clear key and lift out with a piece of hard word.
3. Tap/pull trigger block out.

I have tried tapping the rail back (not too severely, but firmly) after soaking in Plus Gas, but, no movement detected.

Do I understand that by doing the above, not only does the rail move back a touch to clear the keyway, it also pushes the trigger block the same distance, and once the rail it removed, the trigger block can slide out?

Or, do I take the tension on the spring with my compressor against the trigger block, remove the guide/block retaining screw, gradually unwind compressor, and tap rail back to clear keyway at same time, etc?

The leather breech washer supplied by Chambers, does not really fit. Too long, too large outside diameter, too small inner diameter. When I fitted one to my other S60 (non-scope rail), it required a lot of trimming and not easy to do to get close to being OK. The second one bought for this job is also the same. Please, are there alternative seals from other air rifles that fit: 'O' ring, other?

Another question if you don't mind.
I picked up a reasonable and cheap Vulcan from a local auction (furniture, junk, etc)... the white plastic(?) trim seems to be disintegrating, become brittle around it edges - maybe oil contamination? I want to replace it to make it look tidier when I restore it. What material to suggest please? Maybe plastic sheet from a model shop? Other?

Many thanks in anticipation and best regards to all.....