Because leg flexibility is so vital to pulling a good bow and arrow, it is important to stretch your legs in a straddle stretch every day, at least once a day. Make sure to stretch to the left, right and center each time, holding each stretch for at least 15 seconds.
Doing the splits (left, right and center) also will be beneficial to getting your bow and arrow, since a "bow" is essentially a standing left split (or right, if the flyer is standing on the opposite leg).
It can be useful to have a buddy help you stretch. In this single-leg assisted stretch, you are basically doing a bow while lying down. Lie on your back with your legs straight out and have your partner push one leg back toward your head. Hold this stretch for at least 15 seconds.
When you have become flexible enough to pull your leg up high enough for a proper bow and arrow, begin practicing it every day while standing. It may take a lot of practice to balance the stunt properly, but it will come with time.
After perfecting your bow on the ground, you are ready to pull it in your stunt group. It may take several tries before your group makes the stunt stable and elegant, but it will be well worth the hard work when you have finally accomplished it.