[pct-l] new down in sleeping bag

[shon mcganty]

My favorite piece of gear is my lightweight sleeping bag, but over the years it has lost most of its down filling.  Laying in bed during sunrise I can see through the bag and see it really has little down in it (but still works fairly well).
 
I'm considering buying some down online and cutting open the bag and re-stuffing it.  I'm hesitating because I'm worried I'll mess the bag further.
 
So I wanted to throw out a request for experiences or opinions to anyone who has done this.
 
thank you.
 
Shon