Crap. Sometimes you stay away from internet. B.O.R Germany put up a outlet album on Facebook with rims, lovely XMD333 rims that I think is the best clincherrim for mtb, used it last when I was using clinchers. Then I got into their website and found the thing I shouldn’t see:
309XMD Tubular rim that I use now and like for 27,5/650b, should be around 320g so pretty good weight. And then I strangely e-mailed A. Dugast and asked about sizes on tubular tires. 650b tubulars on my Scalpel for next year? Anyone that wants to buy a really nice 26″ tubular wheelset for Lefty?
Tune Cannonball/Kong hubs, 64 DT Revolutionspokes, great FRM 309XMD tubular rims at around 1270g. Anyone?
Link to the rim (also available for 29er): BOR tubular
jonas wwBlog 
Hej Jonas, har du tips på hur jag mäter om min FS 26″ har plats för 650b?
för 2″ däck så behöver du ungefär 35cm plats i radie. Som ett 32mm CXdäck i höjd.
You can put on Tuffo tubulars the 29″ can be mounted on a 27.5″ rim.
No, if you don’t cut it and glue it in right length. 29″ tires are too big