there is a new 29’ rim in KH2017 set-up :
Yes but it’s a non-disc brake rim, and it’s even wider. So whilst it’s good news for our munis, it won’t help my specific setup.
Dear Pierre, this post is related to 29 rims, not only your concern 
To be fair, Pierrox is the OP of this thread and it’s clearly about finding a narrower rim than KH rims for his G29 project, rather than talking about 29 rims in général.
Maybe the title of the thread is not specific enough.
New KH rims will be even wider than what we have now, clearly not matching his project.
What about the rims spec’ed on QX unis?
Or even the Alexrims DX32 that is found on the regular Qu-ax muni?
It is a rim strong enough and in the 32mm ballpark. And they have several different drilling including 36H.
They’re 40mm. (The Plus size ones are wider)
Just for future reference… here is what I did with the brakes as the pads couldn’t reach the rim I settled for (a Rigida Sputnik)!
I ran a Schwalbe Big One 2.35" on a H Plus Son Archetype rim at Unicon 19. It was good enough to come third so I guess it works just fine.
The rim is pretty strong, didn’t notice any flex, and has a braking surface. It is slightly narrower than your Mavic at 23mm. The deeper profile silver finish looks really good though.
Thanks for the feedback!
I kept my Big One until recently. I loved the look of it, the light weight, how I could fall into a turn with it. But I hated that it got 4 punctures in just a few months - the only uni I ever got a flat on. And I didn’t like how it reacted to road camber, and even to tarmac patches (when they fix a part of the road and you ride across, almost parallel, to the joint between the old and new tarmac).
I’m clearly nowhere near you as a rider, but those were too much to cope with for me and I wen’t to a narrower Marathon.