I think that your hair is similar to mine , It's lite and thin and you are going to loose this frontal hairline...looks like your are going to be norwood 3A-3V in the near future, What is your family history BTW? hopefully the meds are going to work for you.
Your plan sounds good, you can definitely wait till age 25 and then do something about it...you will propebly need somewhere between 1200 - 1800 and if you want to get to 80cm2 you will need another session of 1000-1200 grafts. listen to FITLOck and to yourself and stay on the meds, if propecia will not produce good results you can also stimulate your hair growth by adding minoxidil or switch to Avodart after 1-1.5 years.
I will reccomend you to hear also a doctor's opinion, you will be more informative and he can help you to make a good plan for the future.
You can do that by submitting the form that FITLock mentioned in the previous post if you like, We will then follow with your case until or if you will decide to do something with your situation. Good Luck and keep posting
