Hey, I just wanted to add a quick bit to what I said earlier regarding these ki "tricks", such as unliftable body and unbendable arm. In my dojo (kokikai style), the emphasis with these techniques is relaxation! Relax completely and keep one point and they somehow work.
Just tonight, a brown belt weighing about 155 was teaching the basics class. He demonstrated the unliftable body, first showing how much more difficult it was when he shifted his weight down. Then standing upright and very relaxed he was unliftable. Another guy who looked about 200lbs and an ex-boxer was doing the lifting (he's new to aikido). So, I can't say why they work exactly, but they do. It was a great class tonight btw...
Have a good one,
P.S. Great discussion here too btw...