I have never heard of a dealer not allowing hands-on time after a demo! That really is a first for me. I wonder how many cars a dealership would sell if they did not allow buyers to test drive themselves before making a decision???
If you are near a state fair or a large quilt guild show -- dealers often have machines set up for people to sit down and try. At these times you can often get the very lowest sale price possible on a machine, I think because the dealers sell so many machines at these shows they get a bulk discount from their wholesaler. Even if you don't go to the state fair, if you go to a dealership during the fair (and the dealer has a booth at the fair) you can get the sale price.
In any case, I agree with negotiating. Even if you don't feel comfortable dickering about actual price, definitely request add-ons such as additional feet or other accessories. And feel free to walk away to "think about it". You can always come back and say you've decided you want the machine if you can get this and this and this thrown into the deal.