Guides do seem to get paid to use the shops flies (they'll charge you for them at the end, most likely). But if you insist on using your own, you'll get your way.
If you're fishing the 50 Mile Riffle from a boat, 90% of the time the guides will want you to go deep with this.
http://www.mustad.no/www2010/fishing...nth/girdle-bug
It matches the stoneflies in the river.
Rule #1 when fishing from a boat: Keep your flies in the water.
My experience is that the water is so strong and roily in that stretch that nothing much floats. I've have had some success in the 50 Mile Riffle with large caddis with very bright wings. I did have one unbelievable afternoon with the Fat Albert (check out Charlie's Fly Box for instructions).
Streamers can work well. Pitch them out as far as you can and strip them back as fast as you can.