Self Propelled Artillery.

[Epoletov___SPR]

In German OOB, the class "SPA" is vechicle which those were not.
It assault gun and only !

For example: "Brummbaer", " Sturmpanzer IV, "Sturmtiger".

[Epoletov___SPR]

Presence in German OOB of these vechicle in section SPA, gives powerful advantage !
By the same principle add in Soviet OOB in section SPA SU-122, SU-152, ISU-152.
These gun it is rare, but were used as SPA.

And nevertheless it is not historical.
It is better to clean from German section SPA these assault vechicle's.

[Imp]

I would not say really an advantage as low ammo & expensive units so much better cost effective choices. Do agree its wrong though they are assault guns hence the armour.

[Epoletov___SPR]

Add to them "Ammo units" and it will deprive their with one of lacks.

And the main thing - is not historically.