Pila range and how?

[M. Demetrius]

The block of wood holding the flange from the heavy pilum shank rests on the top of the shield, which supports its weight. The thumb simply holds the pilum in place, not support the weight of the pilum. It does not need to be done for extended periods, just long enough to throw the other pilum. Say 15-30 seconds.

Have you actually tried walking a bit, throwing a pilum and successfully negotiating this maneuver while holding a scutum in your left hand? I wasn't able to do it.

And it would take more like ten minutes to get all the soldiers lined up, sorted out, put in place, and advanced to the battle line. 30 seconds isn't enough time. We're dealing with thousands of men, and even one century itself probably occupied nearly the space of a tennis court when in open order.