It's sometimes hard to stall the top of a big top main though. One of their advantages is they allow more twist and are generally more powerful high, and this also makes them more difficult to control off the wind. Not a problem in lighter winds but it would seem that as the wind strength increases and the sheet is cracked, the top twists off and powers up as you bear away driving the lee bow in.
I think that dropping the traveller and leaving the sheet on hard might be the answer in that it would tend to control the twist more. That is if the traveller can operated under the load which is doubtful.

On another note, does anyone jibe their kite on a cat? I mean as opposed to tacking it?