With a very shot axle bow, I don't think you're going to find one that is very shock free. You really need to shoot as many of them as possible to feel for yourself. I've only owned one short axled bow, a 2003 Parker UL 31. Great bow, but the short bows are not very forgiving, so I went to a little longerbow again. IMO the UL-31's after 2003 are not as good.

Of course there is always this 20.5 inch "thing" that you may or may not have seen... http://www.libertyarchery.com/