Out of pure interest...

[bobbin]

True. Hmmm I remember reading somewhere that the Chinese had either bought or captured Roman soldiers from the East and commented on the 'fish-scale' formation they used, ie the testudo.

Thats a very controversial fringe theory based around the description of a Han battle in Sogdia, it's based on some very shakey thinking and most historians don't beileve a word of it. The "fish scale" formation could also be translated as describing a normal shield wall or even just how the soldiers looked like a school of fish.

Concering the OP I agree with Watchman, the chinese crossbow would cause major problems for the roman heavy infantry.