you cant be doing then exactly right then. You need to get a slight bend in the knees b/c you dont want them locked out. Chest out, shoulders back, back arched and bend at the hips. If you can bring the bar to the floor without any or with very little stretch which most people should be able to do especially with a 45 on each side stand up on a box or step to get you higher so when you bring the bar down it does to your toes or as far as you can reach without hurting yourself. Just remember stretching should be apart of everyones workout.
Gary