penetration and crew quality

[Imp]

Crew quality AFAIN does not effect penetration directly but has several effects that contribute to a kill. Namely better rally selection of ammo extra shots & better hit chance due to passing all/more rolls at all ranges, so will hit more often. Close up about 500m the last comes into effect as chance of hitting a weak spot is based on a % of the to hit chance.
So close enough to see the drivers hatch or whatever & accurate enough to hit it hence about 500m normaly.
May also improve chance of a top hit at range from higher elevation unsure though.
However now I have read your post talking 2000m so my thought is diffrent timeframes he had sabot rounds while you dont would account for it.