I wood make the 8 year olds at least 48" long minimum,a lil longer wood be better IMO for that age. My sons 8 and the one i made him a couple years ago is 47" and hes about to outgrow it. You must keep in mind kids grow,so you must make it a lil longer and tiller it out around 4" past there current draw so they can grow with the bow for a few years,instead of it only lasting a year.