It is never too late to learn. After a lot of time spent on fixing the mighty “Flex Printing Engine”(tm), I’ve learnt an important lesson: you have to call validateNow() on parent component as well to get child component properly measured and rendered.
After some research with all these crapy validation stuff I end up with callLater(doAction, paramsArray) function which performs action after complete screen refresh when everything will be redrawn and validated.