While that's true George, loads of folks have Jiris and don't use them as climbing packs. The same goes for Pod and Crux packs too.
I manage to get most of the weight in mine onto the hips without any problems.
You may be ok with one. My back length is about 19" (I think. Pretty hard to measure on your own)
If you really want to try one, and they are a great pack, order one online and send it back if it's not right. It'll cost you the return postage, but that's not going to a lot.