Hi,
How long have you been following the same schedule of transfusion,if it hasn't hindered your growth yet it shouldn't do so now,being said that,i don't think that keeping that low hb is a very good idea,because chronic low hb does damage your body in the long run,i know you are worried about unnecessary iron but when your hb is that low,your body absorbs more iron through the gut,low hb means low oxygen levels in blood and since you work out too,it made me think what if those last week work outs force your heart to work harder with low oxygen,BUT I am no doctor, its just my personal opinion so i think a hematologist might be able to help you more.
Zaini.
P.S whats your weight and how much blood do you take every three weeks?