Some tips are from yesteryear and others from my experience over the last 20 years doing alterations
Sewing rubber backed fabric
Sewing rubber backed fabric can be a nightmare to do. Have you ever tried used baking paper under the rubber? It works well. You could also use brown paper. I haven't tried normal paper, but it could work as well. If the stitching was a straight stitch you would not see the baking paper. It would peel off easily. Happy altering Judith