Re: Side-arm cast woes -- need advice
Another good mental drill is to imagine you're holding a paintbrush with paint on it and trying to fling paint at a target in front of you, as well as one in the exact opposite direction. The motion involved with flinging paint off of a brush is exactly the same as fly casting, because you need to accelerate and then stop hard to send the paint flying.
(I like that example better than the hammering version because the nail/etc generally takes care of the stop for you)
To the OP, I'd recommend gradually transitioning your overhead cast to a sidearm cast, and analyze what changes as you shift it over. Tailing loops are caused by applying power too hard/early in the casting stroke. Going back to the paint brush example, you don't want to start swinging it too hard, in order to make sure you've got maximum paint on the brush when you complete your "fling" at the end of the stroke.
To keep the fly up better, try rolling your thumb upwards as you complete your casting stroke. This should cause the fly to lift slightly upward relative to the water's surface, helping it make it all the way to your target.