FYI, if using a venture crank, you should probably use a crank spacer.
On the new schlumpf, I measured 17.4mm for this 16.0-16.5mm specification.
In addition, my pair of older Venture cranks also do not conform to the ISIS standard,
and measure 17.0mm for this 18.5mm+ specification
Therefore, IMO, a minimum of 0.4mm spacer is needed. Otherwise, the crank bolt will bottom out on the axle before the crank hits the crank stop.
A newer VCX crank I have measured 19.2mm, so that would not bottom out.
Simpler combined drawing of a “normal” interface:
