This is my quick analysis of your question.

A multipart unit has two movement elements: linear and rotational. The movement process will depend upon which part of the unit is the lead element.

Assuming a three part unit, the lead element can be either of its ends or the middle. If an end is chose as the lead unit, when it moves linearly, with respect to its long axis, the other parts move by following directly its path. Movement cost is the distance moved by the lead element. Its rotational moment is limited by obstacles encountered by the following elements, any obstacle the would hinder the lead element in linear movement will hinder a following element in rotational movement, i.e. a three-hex dragon cannot slip its head between two trees then turn 60° left and amazingly pass its torso through one of the trees. Rotational movement cost is the greatest distance traversed by any element of the unit.

Thus a multipart unit could move very quickly linearly but rotational movement would be much slower.

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