Gryph he said front master cylinder. I also talked to a guy who had a sleeving job done by the Guy in South Australia on a Quacker and he was happy. Glen the local guy does not like doing BMW rears due to the fact the plastic is prone to breaking. However if it breaks he machines up a new one in brass complete with an "O" ring seal. He also makes his own imperial pistons and that makes replacement cups cheap. I haven't heard of him doing a shoddy job yet. Surely in the great land of the US there is a competent mob doing stainless sleeving, and there must be more than one even we have two.
Regards Martin.