Jim,
By-pass the salesman - save the commission for yourself. Deal with the Sales Manager or Fleet Manager - whoever the top guy is. That guy works on salary, so no need to jack the price for a commission. Also - no games like - "I have to check with my boss", or "my boss won't go for it"... blah, blah, blah. You want to deal with the decision maker.
When I ordered mine, I got some great info on edmunds.com on how to get a good deal. It worked just like they said. I went to 3 dealers, asked for the head guy, and said this is what I'm going to order - how much? Then I walked - no haggling. They knew I was serious and had only one shot at my business, so they shot me great prices. All 3 were within $20. of each other - right around invoice. I ended up ordering from the guy closest to me - who I wanted to buy it from anyway. It worked great for me. Remember - they make more money ordering one for you than selling off the lot. A truck on the lot costs them interest every day it sits there. An ordered truck never sits on the lot, so they don't pay any interest on it. So they can afford to give you a good price that way.
Good luck! It's a lot of fun!
Dave