Support unit question

[Garth Vader]

If I understand correctly, support units attached to a HQ have a change of being committed if your unit is within 5 hexes of it's HQ. I noticed my Panzer group HQ's have a lot of support units, but since I generally move my HQ's last and the mobile units are fighting further away, should I move those SU's to an infantry HQ where it's CU's will be fighting close to the HQ?

Also I noticed that Panzer group HQ had a lot of pionere SU's attached. They are normally used for assaulting fortified/urban hexes which I would not be going with mobile units. Is there another use for them that I am not aware of?

[gids]

most of the time i put al my arty support in Army hq where they have a chance to be commited in every subordinate HQ battle,jagdpanthers,stugs and pioneres i put in Corps hq.
only when i have somekind of operation i attach units directly at frontline units to break open their front after that i send em back to corps or army HQ,also if you see that SU isnt commited alot ,,take a look at the leader maybe his initative is to low and you can replace him