Make sure that the rubber pads that you ordered are completely rid of the release agent used when molding rubber parts. It's slippery and negates the friction characteristics of the rubber. I'd further rough up the inside of the pads with course Scotchbrite or sand paper to enhance the rubber's coefficient of friction. Of course you will want to check the combined thickness of the glass and the pads compared to the width of the openings in the clamps to ensure that the fit will be tight. If not, you might have to add something to create a snug fit (old credit cards, etc. come in various thicknesses and can be very useful in a number of ways, this being but one). I would only use an adhesive as a last resort as the original design did not use it and if you are using black-edged glass as original, the adhesive could cause deterioration of the edging in short order.
