Put some weight into your BACH pack. Slightly loosen upper and lower load control straps. Put pack on your shoulders and slowly tighten shoulder straps until your pack feels comfortable. If you close hip belt now it will nicely hug your hips. To distribute more weight to your hips, you may loosen shoulder straps slightly.
Position the sliders of the upper load control straps slightly in front of your shoulder as shown in the drawing. The upper load control straps stabilize your load and prevent pack from falling backwards. For best result tighten the upper load control straps slightly.
You may or may not tighten the lower load control straps for firmer fit of the hip belt.