Hi Malcolm,
They were 175mm, I went down to around 150mm... there was a perfect flat area on the drive side at this point but he non-dribe side the cranks taper inwards too early so I made (read bodged) a thin wedge spacer so the pedal has something to tighten against. Was lucky enough to have the cranks lying around and fit only for the bin before this; did destroy a cheap set of shimano cranks playing though.
If I'd have wanted to spend money I junk I'd have bought 140mm ones, they're out there but 50-60+ unless they're made of iron and could be used as anchors!