do you have it in a table or just the machine and extention table sitting on a table with space under the extention to the table surface. If this is the case, I don't know what you might do in order for it not to snag. However, I have read of a system that you can use layers of styrofoam to put on your table top to raise this area in line with the machine and extension table. I believe you would cover the foam extension with heavy plastic sheeting to make it smooth. As I read your question, it does not appear to me that putting a "slider" on top of the machine will help in keeping the quilt from snaggine. Did I miss something in your post. Appears to me you need to raise the table or lower the machine and extension table or just carefully handle the quilt to keep it from snagging. I had a cabinetmaker make me a large additional table that fits over the top of the regular table the height of the machine and its extension. This works great.