I generally shoot with an arm guard. I recently started attending an archery class and none of the instructors wear them. The idea seems to be "if your form is correct, you don't need one".
I believe I have my bow arm set up correctly. The advice I heard is to bend your elbow. If the bow comes up toward your head your elbow is wrong. If the bow swings over toward your chest, you are good. After class, I took my light, 33# longbow to my short range and tried blank bale shooting without the arm guard. I was very careful to make sure my elbow was flexed slightly outward, but got snapped. A dozen arrows and a large goose egg later and I gave up.
Is it possible that guys with a large chest and short arms have things easier than guys like me with a skinny chest and long arms, or am I still doing something really wrong?