The Dualsky was likely an old model, if its the 40A it will have a high quality linear regulator in it and its fine for 4 cells, will drive 4 small servos. The new models of these ESC's now have switchmode BEC's in them, 40 upwards, a good addition as they work extremely well.
My F16 was clocked with professional radar gun last weekend at 146 with a tailwind
Coming out of a shallow dive with about 12mph or so behind her, went past and scared %#!@ out of us!
Cross wind level flight 132-135mph, running around 800 watts right now and uses GWS NARO +F/BB servos