I have the same concerns with my 8 yr old son.  His last 2 labs came back within normal ranges.  The thing that concerns me is that if the 17OHP is  31 or less they dont get a # the lab just says it is within normal ranges.  So I always wonder if it is 0 or closer to 31.  My son is also growing.  We have gone through 3 different doctors over the years and each one seems to manage the disorder differently.  I always wonder what is the right thing to do?  When my son was an infant he too was placed on a large dose and we were told he would grow into it.  I know I haven't been much help, but I do sympathize with you.