I have my eye on this, but the SP page suggests two 50m ropes are needed to rap the West Face. I'm curious whether it's possible to (a) climb and (b) rap this with a single shorter rope (40m), or alternatively if two 35m ropes would suffice for the raps (and be long enough for the leads, obviously).

Thanks in advance.

I can partially answer your question.

There is an intermediate rappel anchor that eliminates the need for two ropes. The rappels bring to the top of some down climbing which can be avoided by rappelling from a fixed anchor on a belay ledge of the Sanchos route (I have never done that - always have just scrambled on down).

I have always used 50m rope, and can't really say if a 40m would work. Two 35m would certainly work on the rappel, but might result in an awkward belay situation on the climb.