If it's less than 5 millimeters you could try your model 66 or your model 15. Neither of them is likely to get harmed even if it turnes out to be too much for them. I've had pieces of wall to wall carpeting edged on some sort of industiral serger, it wasn't too expensive and it lasted well. If you make an attempt remember to use a thick needle and a suitable thread, model 66 can take up to size #22 / 140 needle (Singer model 15 does too, not sure about the badged versions), I have only found this size on the web. Regular #18 is easy to find, top stitch or jeans needle. The under lining on some carpets can be like sewing through eraser rubber, maybe a knife edge leather needle could be an advantage? I expect you need to work a bit with the tension to get it right.