what kind of math are you doing on that and what are you using for your baseline injector size?

last time i talked with RC engineering, the tech looked up the stock injector size on the 420A and it was 234cc.

234cc to 440cc = 88% larger
234cc to 500cc = 113% larger
234cc to 550cc = 135% larger

he said that the stock ECU can compensate for about a 20% increase in injector size. no more. that means anything larger than a 280cc injector would run rich at idle. if you need to go bigger, you'll need an AFC. I'm not sure what the limits of the AFC are though. i never called their tech department.