They sit in very snug on both sides. Build quality and fit is first class, and that is what you should get with a bespoke custom build as these were.
I thought it sat entirely symetrical, but since you asked, I measured it...The right sits 20mm further out than the left, but you have to look very closely to notice. It all fits very close and neat...Almost too close to the indicators.
Shame about that. Have a word with Pete Morecombe at Reboot...He may have something suitable? If not it isn't a complicated part. These are fabricated from 3.5mm plate. They are not identical. They are handed but I didn't measure them prior to assembly. I think there may well be a difference of the order of 10-20mm. If the new cans had been co-operative I would have used them with the standard hangers (with pillion footrests) in the event the mount would have been about 25mm too low, so I went with the supplied supports. (I haven't taken a pillion for the best part of a decade anyway. )
If you need more accurate measurements let me know & I will try my best for you.
Thanks.....I'm sure of it!
Regards,
Nige.