Voluntary crucifixions!? This is news to me, though I shouldn't be surprised.
It was my understanding that Destot's space, which is actually in the heel of the hand between the palm and wrist, is the only place a nail can go without tearing through the hand under the weight of the body. A National Geographic video of the San Fernando crucifixions shows the nails in the palms but the willing victims stand on a small platform (with nails between their toes). However, I've also heard that if the feet are pinned to the sides of the cross then the palms can support the body.
Regardless, thanks for the information; I just ordered The Far Arena.