What!?! Non-welded D-rings? That is some cheap construction there. What you have looks pretty, but definitely not strong. I also notice that it's non-locking which is OK and you might want to do a bit of DIY construction. Some years back I made some cuffs that were both extremely simple, yet extremely strong. I no longer have them (lost them in a move). But I'll try to describe them so you could make your own.

Materials -

1. 2 inch (50 mm) wide flat strapping (nylon or polypropylene) enough to wrap around the wrist or ankle twice per cuff. Something like this.
2. 1 inch or 3/4 inch flat strapping. Same length as above, the actual width determined by the D-rings you purchase.
3. 3/4" or 1" welded D-ring. Make sure that they're welded and not simply bent. Even a solid plastic D-ring is stronger than a bent metal D-ring.
4. 2 inch wide velcro. Length is about half the length of the 2 inch flat strapping.
5. Faux fur for padding. Go for something with a comfortable feel.
6. Strong thread.

Now for the construction of a cuff.

1. Get a length of the wide webbing that's able to wrap around the ankle or wrist TWICE. Seal the edges with heat so it won't unravel later.
2. Now cut a length of the narrow webbing about 2 inches (50 mm) shorter than the length of wide webbing. Pass this narrow webbing through a D-ring, and then sew it to the wide webbing, so that the D-ring is secured to the middle of the wide webbing.
3. Make your padding. What I did was cut a piece of faux fur about 4.5 inches wide (115 mm) and about 1/2 inch (12 mm) longer than needed to wrap around the ankle or wrist. I then folded it in half length wise and sewed along the long edge to make a tube that was furry inside. I left about 1 inch in the middle of the seam un-sewn. After the long edge was sewn, I then sewed the two ends of the tube closed with the long seam running down the middle. After both ends were sewn, I then turned the entire thing inside out using the un-sewn section of the long seam as a hole to pass everything through. This will result in a furry flat piece of cloth that can wrap around your wrist or ankle once.
4. Sew your padding to your cuff. Simply sew the padding the wide webbing on the side opposite the D-ring. This will result in that side of the cuff being half furry padding and half raw webbing. don't worry too much about making it extremely secure since when you sew on the loop velcro later, you'll also be sewing through the padding, making it more secure.
5. Sew your hook velcro to your cuff. Simply cover the raw webbing on the same side as the padding with hook velcro. Be sure to use plenty of thread. This will be the most annoying part of the job since the hook velcro tends to catch the thread as you're sewing.
6. Sew your loop velcro to your cuff. Simply cover the raw webbing on the same side as the D-ring, opposite the faux fur padding. Once again, use plenty of thread.

And you're finished. When you wrap the cuff around a limb, it will go almost twice around the limb, and the amount of velcro will be enough to go almost around the entire limb once. When the submissive tugs on the cuff, almost all of that velcro will be placed under sheer tension which is what velcro is strongest against. To be honest, the cuffs should be strong enough to support several times the body weight of your submissive, although I would NOT recommend using them for suspension because the direction of the stress would be likely to cause injury. But as long as the submissive isn't able to pull on an edge, they're not gonna break those cuffs.

Poor ASCII art of side view of cuff.

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1 = loop velcro - covering half of the top surface of the cuff.

2 = narrow flat strapping. This holds the D-ring to the cuff. The D-ring is located in the middle of the cuff, where the loop velcro ends.

3 = wide flat strapping. This provides structure to the cuff.

4 = padding

5 = hook velcro