I have always played sitting but with the bass standing up almost entirely straight. Ive always experienced discomfort in my left shoulder, upper back and always felt the strings were difficult to hold down. I use the muscles in my arm and back to pull back on the string but what ive come to understand is that when the bass is tall you experience a fundamental issue. You are pulling an object away and not down therefore creating the same effect as pulling a rope from a wall but having o hold it up. The further the bass goes to the side the less it benefits from falling naturaly into your lap, stomach etc. by allowing the bass to fall and by positiong youself behind it you are taking advantage of gravity. Simply by placing your left hand on the strings this way is almost enougj force to press them down. Thoughts?