Not entirely sure what you want, you don't say whether the controller is linear or PWM
If it is linear, what you have is a 'sort of' regulator, if so you may be able to get more poke out of it by the usual method of a bypass transistor(s).
Download the pdf for a L200, and look at fig 21. It shows a 2.5 Ohm resistor before the regulator. This will switch on the bypass transistor at around 280mA or so.
The remainder of the current drawn will go through the bypass transistor.
Just a suggestion of where you MAY find an answer. I've certainly used a L200 as a motor speed controller many times, including with the bypass wotsit. Up to 10A or so. You will need a circuit breaker/fuse, because you will lose the current limit I think. Not through the controller, but through the bypass.
Other than that, you'll have to be a lot more specific.
**broken link removed**