With this mentality^^, your bike would never be light. I'm not big on cutting weight simply because im fat, but if i were seriously trying to shed weight i would totally run a front caliper on the rear, even if its a 1/2lb. Shit adds up quick.
Im sure it would fit. But it will not work right at all. For starters the shock will be at such a hard angle it will not be effective. And depending on the length of arm, the valving will be all f'ed up.