In reply to AMorris:
Full circuit of The Arches traverse, Lady Bay Bridge, Nottingham, roughly V4 5c, took me over a year of occasional but increasing effort. The week after I did it they took loads of the holds off then they ruined a lot of the best stonework by painting it.
I wouldn't work a problem on real rock as its seems a bit unethical in terms of wear and tear and very expensive on petrol.