not sure about your extension table, but i have an 'aftermarket' one. it fits my machine bed, but there are 'bumps' where the two join. this totally eliminates that and seems to give the bed just the right 'touch' to make me more comfortable with free motion (and i've had my issues, believe me!).
i'm not sure that it's actually 'static cling' (on the bottom side). it's more of a sticky plastic finish that kind of reminds me of what the acrylic stamps are made of (for card making, that cling to the acrylic block so you don't have to use adhesive). the top side is the teflon finish (so they say, you could fool me easily enough) that is really 'slippery'.
and something else that makes me think it's like the acrylic stamp finish is that the directions say if it becomes 'nonsticky' gently wash it with warm soapy water.
hope this helps!