Am sure have read this somewhere - but simply can not find it today.
From memory (and don't trast that) .... a unit can shrink frontage during a charge to avoid bad going or friends ? yes/no

Page 119.

Can contract by 1 file to avoid friends as long as they remain at least 2 files wide - NB not to avoid terrain for which they "only" have the 1/2 BW universal shift.