I was quite interested in this topic a while ago.........and did quite a bit of research.
It seems bizarre that Witnesses examine scriptures to the smallest detail, but when it comes to the evidence right in the gospels, their reasoning goes out the window.
Matt. 27: 37 has Pilate putting the infamous sign above Jesus' head, not his hands.
And I think it's been mentioned about Thomas exclamation of "seeing the print of the NAILS in Jesus' hands.......yet in every picture portrayed in the literature they show one nail.
I've also read that it would be far more difficult to stay alive for very long if your arms were fastened above your head in that manner........very difficult to breathe, not to mention your arms losing all circulation. Yet the whole point of this manner of death was to make it last for some time.
A recent article on this (March 1, 2008 Watchtower) mentions on pg. 22.............."more important, no matter what device was used fopr the torture and execution of Jesus, no image or symgoll of it should become an object of devotion or worship for Christians." (the article still mentions the argument of the stauros, etc. but it seems to give the impression they're not so dogmatic about the topic)