[rdorman]

How far back? Pivot at the back of the foot box! Well, not really. But what you don't want to do is have the pedals over center in relationship to the plain in which you are applying pressure. Simplified, you don't want the pedals to go past the point that is 90 degrees from the line drawn from your hip to the pedal... you loose leverage after that point. Pedal travel through an arc which changes the pedal ratio. Put in a heal brace and positive stops for the clutch and gas (unless you have them else where) as well. Make the box so that it can be easily moved forward and back.