Apachie, how exactly do you hold his feet? You may want to raise them just a little bit and keep straight under his body for his comfort. Also you may want pick the hoofs placing him against the wall (in stall or shed), which would also help with balance.
BTW, my well balanced in general paint loosing her balance almost every time the farrier raises her back feet or stretches her. In fact 1st time ever he did stretching on her front hoof she fell on him. That was very scary (and he doesn't try it any more). Interesting enough she does hold her balance when I trim or clean her (and just to add, she's not misbehaving or showing off, but loosing her balance indeed when the farrier does it).
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