This is ridiculously timely: I came searching for exactly this issue as I have two orange SONAX 6.5" pads with the cloth backing coming off this past weekend. The foam is still in great shape, but I have a hard time controlling the pad placement on the car with half the cloth coming unglued. My Lake Country white pads have been holding up fine.
I have access to a hot glue gun at work; how heavy/thick an application are you suggesting?
I was doing a search of the forum and found one member had used hot glue to bond the velcro back together, he didnt say how much or what kind of pattern.
I have used 3M spray trim adhesive glue to a couple of pads, but one is ready to let go after some use. I have seen anything from gorilla glue, super glue, and hot glue listed. I love the 6.5 CCS pads, I just ordered 12 more, but I would really like to save these too, much more life left in them. It alomst looks like some kind of rubber cement type of adesive used to bond the velcro to foam. My orange pad had the glue peel off of the backing pad in one piece,
( it was funny , the foam took off and I couldnt find it anywere, two days later it was on the roof of my other van, Im a T-7 para in a wheelchair, my neighbor asked me, "whats that orange thing on your roof....lol.).
I always wash and set them face down to dry, and use a rolling pin to exrtract any excess water. I also found out that twisting up the pad to dry and hot water seems to be bad on a pad too. I still think this is the best pad for my needs.