Having gone through the First Osage for my First Bow not to long ago.
I recommend you build a board bow or two first.
They tend to be cheap and if you break one or come in under weight on another you are only out some time and the cost of the board.
If you are bent on your Osage stave being your first bow, Go Slow, Double Check your design Twice, and measure Four times before you make Each cut.
And use your scraper more then your drawknife, unless you are quite friendly with your drawknife.
Best of Luck to you.
-gus