In short, I was wrong.
The Posable Mctoran™
now has fully articulated legs allowing for sitting, walking and running. No longer must he shamefully shuffle along the ground like his brethren, for he has been cured of notbeingabletowalkproperly disease with one obscure piece:
The Lego Football goalkeeper holder. It’s a really weird piece, but it allows both legs to be slotted in easily and without restricting movement. One of the bar connectors simply plugs into the bottom of the torso piece. Unfortunately this piece only comes in red and dark gray, so for all other types of Matoran it may look a bit out of place.
As a side note, the Posable McToran™ can now actually pilot the Boxor better than a regular McToran, as he can both sit in the cockpit instead of just hang there, and most importantly he can reach and grasp the control sticks.
The Posable McToran™
still remains roughly the same size as a regular McToran despite his upgrades.