If you can locate a vintage 6400 series Viking sewing machine from the 1970s in good working condition, it will sew over many, many layers without hesitation. I did a lot of sewing with multiple layers of heavy decorating and upholstery fabrics and was never disappointed. It is a heavy metal machine that doesn't slide around as you sew. The only drawback is that Viking parts are getting harder to find if you need to replace them as they aren't making repair parts any longer. I'd suggest finding an old-school repairman and tell him what you are looking for, he may have a good machine available in his stash that someone didn't want to pay to have repaired and now runs fine.