I have the same problem and I am going to try the Walmart shelf paper: Many thanks: I tried the mouse pad: Did not work for me either:::

I put sticky velcro on the bottom of the pedal and it holds it to the carpet. If you don't have carpet there is a product call stay pedal that you can get, under $20.00 at Joann's or Hancocks, cheaper with a coupon. It's basically a mat that the velcro will stick to-----
I too have a 6600 and I learned to use the stop/start button and don't even use the foot pedal. It was ackward at first but once you get the hang of it,----wonderful-----
I have fibromyalgia, bursitis in my hips and sciatia so this has been a life saver for my back and hips----Give it a shot and don't give up----

I found a placemat size at the dollar store. Works great!

I also have a Janome. I put velcro on the pedal and put it on a mouse pad. It sets on a plastic mat. Never moves, does great.

OK, y'all are gonna think this is crazy, but it works for me, for both my sewing machine and my serger:

cover a brick in aluminum foil & put it on the floor, a little behind where the foot pedal is comfortable. Put the foot pedal in front, up against the brick, and sew to your heart's content. The pedal will not stray, I promise! :)

I use the rubber shelf liner and it works fairly well. Occasionally, I have to readjust, but it usually stays in place.

I have never heard of the brick method, but it is crazy enough to work. I have laminate floor in my sewing room. Even with the pedal pad I bought from Connecting Threads, it still moves. My machine is a 6600 too. I just may have to get a brick.

Presently using the placemat but still find the foot walking away.

Cheaper at the $$ store.

Another cheap WalMart fix....there is a rubber mesh backing that is sold to put under throw rugs to keep them in place. Get a piece of that and cut it to the size you need. It's a huge piece but it's cheap and will definitely work! (Then cut pieces for the rest of your friends or for the bottoms of slippers when you make them....)