feline fanatic

For a true stitch regulator the machine's needle will only stitch when you move the machine so a foot control or simple on off should not make any difference. If you are getting varied stitch lengths it sounds to me like what you have is not a true stitch regulator (if the machine isn't moving the needle isn't moving) but sounds more like you have a speed control. I don't see anyway you can put a foot pedal on a rack mounted setup. The machine head is constantly moving the length of the rack. The foot controller could only work if you had the machine stationary in a table. Also where would the wires go?? So without knowing this machine I would have to say the short answer is no you can't use a foot controller on a rack mounted machine.

All that said, I strongly suspect the Sew Control is more of a speed setting than a true stitch regulator, especially when brand new it is offered on their website at only $600. Even if it is a true SR, it probably isn't very advanced or responsive of a unit so your speed will come into play, especially if you slow down and speed up quickly or make abrupt moves. I wouldn't expect a lot of responsiveness out of the Bailey Sew Control, you can only buy so much electronics, encoder and computer for $599. Your best bet is to just practice with it until you find a comfortable speed setting for your movements. Also watch how fast you come out of a dead stop, that usually results in a long stitch. Likewise if you make a sweeping curve very fast then slow down abruptly that results in shorter stitches. Also there are varying qualities of stitch regulators on the market. Some are very responsive, others, not so much. The super responsive ones cost in the thousands. In the case of stitch regulators you pretty much do get what you pay for.