Joe, I have seen pictures of English carriage bows that were hinged at the center, and folded up (back-to-back) for transportation. If your two limbs butt perfectly against each other, and the handle area is stiff, then I would think the forces would transfer smoothly from one limb to the other, and your sleeve just adds stability. I could be wrong, though. Seems to me, if I used a bone collar, I might think about wrapping that in rawhide, both for looks and for something to grip, as well as the added safety.
Sleek, if that bow is for me, I vote keep the knot.