A unit is hit by a rear charges .
2 files are impacted
The unlucky player wants to conform and by doing so reduce the impact to one file
May he so reduce the charge from 2 files to one file only ?
Elements contacted on a flank or rear cannot align.
The aligning for combat rules talk about moving a front base to align with enemy. A unit hit in the rear would need to align its rear bases so conforming will not apply to them as they are not front bases.
However, based on the wording if they are just 1 base deep you could argue that they can align as they are the front bases* and could align to have just 1 base in contact as there is nothing saying you have to keep the same number of bases in contact (although there are rules about entirely breaking contact).
I would rule per RJC based on intent as I understand it.
* 6 C 3.1 does not talk about front edge unlike 6 C 3.2; I suspect this is a wording omission and what RJC has posted in the intent.