I think 19x43 is lowest gearing without changing the chain... IIRC that is what I have in my Dragon.
EDIT: Looking at the service manual, for the trail sleds in IQ chassis in 07-08, it shows a 21-44 ratio with 78 pitch chain... so a 44 might fit, not sure if you could get the tension you need with a 78 pitch chain since you would probably be wanting a 19 top sprocket not a 21...