I have a Queen Supreme Slider. The hole is not centered in this size slider. The following measurements are to the
center of the hole.
When the slider is oriented horizontally (so the length is running left to right), the hole is 6 7/8" from one side and 9 7/8" from the other.
If the slider is oriented vertically (the length running front to back), the hole is 5 3/4" from either side.
I have a Pfaff Performance 5.0. When I place the Slider horizontally with the 9 7/8" to the right of the hole, it fits perfectly.
Two other less expensive options you might try are:
http://forum.missouriquiltco.com/loo...esome-fmq.html
http://thequiltrat.blogspot.com/search/label/sew%20slip
I recently bought an oven liner and plan to give the first option a try as my machine is in a cabinet with a plexiglass insert (like the original poster) and I wanted to cover the entire area too.
Hope this helps.