I looked into coopers a lot, generally you hear they are difficult & hit/miss, but there just hasn't been enough widely flown in uk (rather than sitting in breeding pens) to get a good idea, but they do well in the states with passage birds which is preferred, captive bred seem mental!
A nice male harris really is a pleasure.....I even took mine on a camping/hunting trip to the New Forest....no bother....it broke him to horses lol