[NASSTY]

To concur with Les,

The whole point/simplicity of the Jag IRS is that as the half shafts also double up as the top arm of the suspension. Therefore the driveshafts must be equal in length for the IRS to work properly/evenly on both sides. As a result the pinion must be offset so that the crown wheel is in the middle of the axle in order for the half shafts to be equal in length.

This offset doesn't matter as you want the uni's on the drive shaft to rotate or else they will not be lubricated properly.

What does matter is that the horizontal and the vertical plains of the pinion to the tail housing of the tranny are the same.