Those are great numbers for just starting to box squat. You need to use the same form whether you are squatting 135 lbs. or 335 lbs. If you want to really target the hips & hams then you need to use as wide a stance as possible. The wider your stance the harder it is to make it down to parallel so you have to find a happy medium. Now, when you return to regular competition squatting you have to use the same form as if you had a box underneath you. If you change your form (i.e. bringing your stance in, not sitting back, not pushing out on your knees, etc...) when compettition squatting you will not have a significant carry-over. Be sure to always use the same form. One more suggestion I have for you is to not worry about repping the weight. You will be much better off just hitting triples and increasing the weight until you fail and then start hitting singles until you fail. This way you can focus on your form and move into even heavier weight. Too many times when repping weights the form suffers at the end of the set due to fatigue, loss of focus, etc... One more thing: if you have chains and bands; use them. They are tremendous tools for gaining strength and size. Good luck!