"A second area of concern was whether the preventer should be attached to the outward end of the boom, or at some midpoint on the boom. There was no consensus here, although the end of the boom seem to be slightly favored, but many with mid boom travelers attach to mid boom (I use mid boom). "
On another discussion it was suggested to have a line, attached to the boom end, ending in a bowline at the mid-boom point. Some shock cord would hold it to the boom when not in use. You could attach your gybe-preventer's shackle to the bowline.
What do you think?