Originally Posted by TobyStephenson

when you run the wide hub, you run narrower hexes, such as -2, to keep same overall width

take a look on petit for Ben Smith setup at Herts last year as an example. You do need the dirt inserts to achieve the “later” letter settings and depending on what you run, different length driveshafts may be required to retain correct engagement in the drive cup. I think it might be the dirt car UJs in this case.