Holding a spear in phalanx, a technical question

[aktarian]

OK, this is one of those details that keep bugging me and can't find an answer.

When holding a spear in "ready" or "travelling" position one holds it with palm facing inward and thumb on top, that is toward the tip. However in order to raise it above the shield one has to grip it so that thumb is facing toward the bottom, in other direction. Any ideas how hoplites changed the grip. Anything I can think of would require lots of movement and waving of the spear around, something one couldn't do in compact phalanx.

Any ideas?