Yeah, there is a lot of Crepe Myrtle down here in Fla.
Let us know how the bow build goes.  It is a very hard wood!  I would imagine the grain is not for a beginner!
The arrows should pretty strong, but I would imagine they would be heavy.  Let us know how it goes with both projects.  An aside note, the leaves are supposed to be good for diabetics, when made into a tea.  I have tried it, and it is not unpalatable, but you could mix it with regular tea.  It is an Indian(India) herbal remedy, called Banaba, or something like that.  There are a couple of species of Crepe Myrtle, the ones in India, are huge, like the  Giant Sequoias. 

  Keep us updated. 

                                   Wayne