In reply to harry 600:
You need to be clearer about what you mean by
> lead (twin rope) with one, single rope
You mean lead on a doubled single rope clipping it as a twin, i.e. both strands into every quickdraw? Why on earth do they want to do that?
If the rope is triple certified as a twin then I suppose there'd be no obvious safety argument against it as long as they're sure it's long enough to lower off doubled.
Impact forces in falls will be a lot higher than using it as a single - I recall reading somewhere the 1.4x the single impact force is a realistic figure, not double - but that shouldn't be such a big deal with typical climbing wall fall factors on bolts.
Or do you mean they want to lead on one twin rope? In which case no way, and your wall would probably be in deep trouble liability wise if you knowingly allowed such a thing.
Post edited at 21:53