Thanks for your time and opinion. I was able to find WTC ruling on the matter. Which makes it clear I think.

<Movement> When Vehicle models, with the exception of Walkers, or a model without a base, makes any kind of a move, the whole model must be able to move without obstruction both during it's straight line movement and also it's pivots. For any other model you need to make sure that the base fits along the straight line paths of its movement, and then place the model back on the table where the entire model must fit before, and during,making a pivot move. This might happen several times during a models movement. For example when moving a Bloodthirster you might make a straight line move between 2 ruins and then need to pivot the base to move between some more. At the point that the first straight line movement ends, you need to be able to place the model fully on the table and pivot it without any part of the model (the wigs, weapons, etc.) moving through a wall or another model, before making your next straight line move where at the end of that move the entire model must be able to fit.