[Nasher]

Only the 748R and 998R had the 15mm offset discs, not the 'lesser' versions, the 'R' is key.

I think it's because they were fitted with Ohlins Forks(pre-Radial), and the caliper brackets put the Calipers further out.

I've just measured a spare set of Brembo discs that came off my M1000 and they are @10mm offset.
I need to make sure the 'R' discs are measured the same, but have popped off a message to the guy I know has some and asked him to measure them.

Some additional info.
Your disc carriers look quite chunky.
The Brembo ones on my 1000SS and M1000 are both only @4.5mm thick.

I also removed a disc bolt from my 999, which has the low profile domed heads bolts I linked.
The head is just 4.2mm high when fitted.
Your nice shiny ones look a lot higher than that.

On the 999 they are fitted inside deep pockets in the Disc carrier, and only protrude @2mm.
The 999 discs are still only @5mm thick, so at the bottom of the pockets are only @3.8mm thick.
I wonder if you could get your discs pocketed to around the same thickness.

Aaagghhhrrrrrr, why aren't you closer?
This is the sort of 5h1t that keeps me alive, I'd have the whole front end of your bike in my garage by now working a solution if I could.