'Did you sew the rug on the Sapphire? I wouldn't consider the rugs the heaviest thing I've fed through my sewing machine (thick, but not terribly stiff).
If you did your rug on that machine, it should give you an idea, at least, of what your machine is willing to handle. I have a friend who sews on Pfaff's that couldn't get through multiple layers of fabric and stiff interfacing when making bags, but she did a rug without any problem.