I know this is an old thread but thought you might like to know that a synthetic version of the fairfax has now been made. Endorsed by fairfax and made with prolite. They are just under £90 which while still a lot of money for a girth would probably be worth it IF they did make a difference to your horse.
It's currently the plan LF Depends on the house move and work, but hopefully a nice ID or similar will be joining the Hairy Gang . All low level stuff and lots of hacking, with D on his pushbike and the dogs running with us