Join Date: Mar 2009
Location: Central Iowa, USA
There's a whole bunch of things that go into loping - most of all is relaxation and impulsion. Loping slow doesn't mean cantering lazy.
So, like Ian asked - is your horse comfortable "loping/cantering" at his natural pace at a consistent, "self carried" (ie on a loose rein) manner? If not, that's your first hurdle.
Generally, a lope isn't actually shortening a horse stride all that much (maybe slightly, but you don't want a choppy, short gait) - it's getting them to slow their legs down but still have the reach with their stride.