Has anyone fitted one to a BSF?

After the recent S54 thread I dug mine out to check it over and it wouldn't pull the skin off a rice pudding. A strip down revealed that the leather head had swollen and could only be moved with light taps from a hammer. Sizing it has helped but I'm no fan of leather so have ordered one of the above seals from Oz.
Anyone got experience of fitting one in a BSF or should I be classed as a heretic and horse whipped for even thinking of modifying an S54 in this way?
Cheers
Dave