Scott,
How many fish do you expect on that fly before the legs are gone or too mangled to work? Although you wouldn't get those hairy "knees", I can't help but think that Antron fibers etc... would make much more durable legs.
But it is a beautiful fly. Alan's "Mike" must be an angler of good taste.
Could you spare us a link to the Caithness site?
Regards,
Ed
edit: Thinking about it. running a couple of black Antron fibers down the pheasant tail fiber before knotting might also add a lot of durability, if you don't purchase the pre-knotted feathers. That would still give the hairy quality but might give some reinforcement.