Well, it does depend on the machine you're using. With the Bernina's stitch regulator (BSR), you set the stitch length to whatever you want, and move the fabric at any speed, and you will get even stitches.

I use 0.

I use 0 too. I know it doesn't matter because the feed dogs are down, but it keeps the dogs from moving under the plate. :-)

originally it was said to set it at zero but now i just leave it set at what ever it was. it doesnt' matter at all really. you control the length of your stitches by your movement of the quilt under the needle. slower makes smaller stithes and faster makes longer ones.
fairly fast foot pedal speed and slower quilt movement makes nice FMQ look.

When doing free motion remember this simple formula...your pedal to the metal you hands on Prozac. The machine sews fast your hands go slow. Find your own rhythm and practice makes perfect...if you are haveing trouble in the curves is is because we tend to speed up when sewing up...at least I do. Something to work on.

Try this link for info. She is incredible!!
http://www.daystyledesigns.com

I'm not an expert in any sense on this but I have found if I set my machine at a slower sewing pace (because I find my foot pressing so hard on the peddle I lose control) this way my speed on the machine is the same no matter how "HEAVY" my foot gets.

The shop where I got my machine said to set the speed on a slower one and then mash the foot pedal so that I only have to think about the speed of my hands fluctuating.

Stitch length in fm is regulated by how fast the machine is going, and how fast your hands are moving the fabric under the needle. You learn to keep your stitches the right length. It just takes practice, practice, and more practice. have fun

When the feed dogs don't move, it saves wear and tear on that part of the machine. But yes, since the dogs are down, it doesn't really matter what at what length you have the stitch set. It is really just to save the mechanism that runs the dogs.