A month or so before my first comp, I was talking with a guy (who'd won at least one Jr. Amateur championship) and, happening to have my journal with me, I showed him my pix with my then appallingly pathetic attempts at posing.
After he got done laughing, he gave me a very helpful piece of advice for the side tri -- at least, I found it helpful. He said, instead of grabbing the whole hand, grasp only the first two fingers of your downstage, or front, hand, in your upstage, or rear hand. That allows you much more flexibility in how to position your arm for best flexing, since you can rotate your fingers any way you like in the fist of your other hand. Plus it does not bind the arm as tightly.
Just try to remember to sort of curl up the other fingers and thumb, so that they are not sticking out behind your bum in an unaesthetic manner.