Obviously the driveside endcaps are different between Shimano and XD freehubs, but does anyone know for sure if the NDS is any different? Surely NDS must be the same to avoid messing up rotor spacing… ?

Correct, only DS changes

And if you’re going Shimano to SRAM you can just file/sand around the end cap until it fits. Works grand.

Just taken a look at the end cap after the sanding suggestion.

There’s no scope on the rear as it is entirely bearing shield so it would need to be the outside face. Does it not cause issues removing the surface serration? How much roughly needs to come off?

The height dimensions are the same, it’s just the diameter of the flange that differes. BSM is suggesting reducing the diameter of the flange.
There is a small difference in the two end cap faces that touch the bearings though..

Aha. I assumed it was like the hope situation where using a Shimano endcap on XD creates bizarre FH not FH’ing faults similar to forgetting the spacer behind the FH body. Okay, if it’s precision re-shaping of the flange that keeps the weather off the bearing seals I’ll probably just bite the bullet and get the correct cap…

Ta!