I always had trouble with my quilt hanging up on the edges of my extension tables. My machine sits flush now and it's SO much easier for me. I still hunch up my shoulders (bad habit) so now I'm experimenting with sitting on a balance ball - I'm forced to keep my shoulders back further or I lose balance. It seems to be helping but still pretty new so not sure about it yet.
I've heard of people "tenting" their extension tables - get a piece of slick vinyl and put it over the extension (cut a hole for your needle) and fasten it down to your tabletop around the edges so it's pulled taut and sort of makes ramps on the sides of your extension, so there's no place for anything to snag. That might help, until you can get your machine set into a table.