model_flexi vs model_flexi_m?

[player1]

What exactly is the difference between those two ways of defining CAS model.

I did noticed that model_flexi_m helped in several bugged BI units like Praeventores, but I still not have idea what does it do differently then model_flexi.

While experimenting for most units it did no difference.

[tFighterPilot]

If there is no M, parts of the model that are not part of the body will not be rendered.

[player1]

Well, that explains how Praeventores got visible again after I added them M.
It seems whoever made model thought that arms and hands are not part of the body.