Most people use D Rings. I didn't. And I would recommend against them to avoid having metal dig into your scalp.
Here's my particular method:
As you can see in the second picture, there's no D ring on mine. I had some straps lying around the house that I'd previously purchased from Home Depot:
These straps were the perfect width and I just cut it to length. The real magic is where that orange stitching is. That strap kind of folds over on itself and the orange stitching is what fastens it together. I strategically cut one end of my strap just south of where all that stitching is. So on one end of my strap, it's really thick on the end. It's too thick (on that end) to pass through the rod mechanism on the Quest. I can tug as hard as I can, and I won't be able to pull it through (thanks to the strategic place I cut it). And then on the other end, I just attached high strength Velcro tape and attached it to the Velcro on the DAS strap. Simple. Cheap. Comfortable.
P.S. The DAS Frankenmod lives and dies with a counter-weight. Either Velcro a battery pack or 200 grams of something onto the back. It's the rigid design and that counter-weight which removes the weight from your face.
