It can be a matter of personal preference. The batting will make it harder if you use stemmed goblets to keep them from tipping over but if you use water glasses that shouldn't be a problem. There are also some other types of things you can use in place mats. One I've seen in quilt shops but I don't remember the name of it but it comes in packages of 4 and is cut to the shape of a placemat. You quilt directly on it. Perhaps someone else on the board has used it or know the name. There is also a material called "stiff stuff" which is good for placemats. It is a cross between an interfacing and batting. It gives the place mat substance without much puffiness and you can quilt through it. Personally I think two pieces of fabric would be too thin for my taste so I either use a low loft batting or stiff stuff in mine.