C.M.
I am in the process of making some hardwood shoot arrows and they need more straightening than any dowel you would consider for an arrow. I am using the heat gun and pressure method and having great success.
Couple of things I've picked up.
-Do your straightening in a couple of sessions. Get rid of main bends, then go back and straighten, then some more and finally get them arrow straight.
-when done with a session, leave them on a flat surface so gravity and their own weight don't reshape them while they cool.
-Don't test their spine while they are still warm. Got myself a thin round boomerang the other day doing that one.
Dowels can make great arrows, sometimes. Watch the grain and check/test them real careful before shooting them. I've had several come apart on me, luckily no injuries.
Good luck and so us some photo's of your finished products.