I think you are right in that it could be the needle is too small. A size 10 needle is the equivalent to a 70 needle which would be used for cotton and thinner thread than upholstery thread. I don't know what material he is stitching on nor the size of the upholstery thread he is using. The picture of the needle package is a German made needle. They make many different sizes and types of needles The ones I use are round shank and used in my long arm.