Oh yeah pads are slammed right to the top and it's not optimal, but the difference you need to clear is only about 12.5mm of vertical adjustment (650b = 584mm 26"= 559mm).
the 42c I'm running makes the entire wheel diameter about equal to a 26x2, so geo isn't effected too much either.
Cool, I would have thought the rim diameter would've been too different. Might try it one day!