If you wipe the underside of the Slider with a damp cloth, its grip improves considerably.
Silicone spray is a good suggeastion too. I spray some onto a cloth then wipe the machine bed, rather than risk spraying the stuff into the motor.
Thanks for the suggestion of painters tape to stick down an oven liner -will give that a go.
I too always have the feeddogs up these days when FMQ'ing - I agree that it helps the tension. But it probably varies from one machine to another.