Do you try to muscle the swing to create more revs? A friend of mine tends to bend his elbow, too, and he goes deep into his knees when he releases the ball. I guess it is an subconscious attempt to put more power into the ball, which is normally not necessary.
Well, this is a stroker's point of view: For a straight arm and a more controllable release, just let the weight of the ball direct your pendulum. Start with an adress position holding the ball at waist height and start your move with a gentle ball movement as if you would place it on a table, at the same time starting your initial step (4 step approach). After this start, do not use any force on the ball on its way until you release it. Let it flow naturally with your footwork, the ball should reach shoulder height at the back of its swing. Just let the ball come down by its own until it arrives at the bottom of the swing at your ankle. Then, when the thumb is gone, you CAN accelerate your swing, curl your fingers and bend your elbow, but NOT before. Anything else will irritate your swing.
If you need more speed, simply try a higher adress position. Gravity will do the rest (it is a powerful firend to have in bowling), and I suppose this will be less tiring to your arm and hand than your usual practice.
And check the correct span and pitche sof your ball. If you cannot grab it comfortably, something will go sour to compensate. Maybe you bend your elbow because you have to support the ball on its downswing with the cup of your hand, because it is too loose?
Hope this helps?
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DizzyFugu --- Reporting from Germany
"All that we see or seem, is but a dream within a dream..." - Edgar Allen Poe
