I have a Crooked Horn® binocular harness, which is a really good product, but I have found it hard to use while wearing my treestand safety harness. My idea was to make a quick-connect system that holds my binoculars to my safety harness.
I collect all the speed clips I come across, and if they're on web straps that's a bonus. You can buy a 1" wide web strap with a speed clip at WalMart for $1.97 in the camping section. Attach one side of the speed clip to each shoulder strap on the safety harness, and attach the other half of the clip to a strap on the binoculars. Make sure the straps are long enough that you can bring the binoculars up to your eyes and use them comfortably.
With this arrangement I can quickly connect the binoculars to the safety harness as needed and the safety harness does the work holding them. No need for a second harness, no strap digging into my neck and no long binocular strap to wrap around and take up room in my fanny pack. The binoculars won't be held tight against your torso, so be careful moving around as they might swing.
As you can see, I have a Robinson Outdoors Spider Harness®. With this harness I didn't have to do any sewing, everything just buckled in nicely. With a needle and thread you could do the same thing with just about any safety harness.