[Rules] Disrupting Tank Riders

[Poor Yorek]

Mike,

If you return to look at this thread, I have another question along this line:

Suppose there is a GREN being transported by a good order tank in a hex with: (1) a reduced HMG and (2) a DIS or DEM gun (mostly, I care about the reduced and morale status).

So now suppose that, for whatever reason, the foot unit riding the tank is forced to unload in that hex (the other units still present) bringing about a conflict with the stacking limits.

1. Does the formerly transported GREN *have* to be eliminated or
2. Can the owning player choose to eliminate either the reduced HMG or the DIS/DEM gun?

In other words, when unloading causes a stacking overload, can the owning player freely determine what unit(s) to lose or must the unit that "caused" the stacking overload (here the tank riding unit) be eliminated?

Thank you.