I don;t think the actual CFM will change, the CFT will just make it come on faster at a lower feed rate. The actual CFM will vary with feed rate, so unless you crank up the thermostat to make the feed rate rise, therefore, the CFM will increase.
I know what you are saying, I normally just put mine on MANUAL (FSM) and set the blowers about 50% to help move the air faster for a while, if the Feed rate goes above the limit the fans are set at, it will automatically go back to normal. Then I put it back after 20-30 mins and it does raise the temp 1-2 degrees in the living room faster.
Maybe Paul @ Coaltrol can shed some light if there is an advanced setting to change the Fan Speed based on Feed rate or something?