Joe, been there-- done that. Not just on the first GRTIII install on my CFX, but also on my 440. Just as you, though, both times I was aiming at the target for the first shot and hit it, just not where I had expected to. The feel is just so much lighter and smoother than the stock trigger that it's almost impossible to avoid overpulling that first shot (not to mention that big stupid grin on one's face after realizing how much of an improvement it is).
Of course, as Big Bill rightly says, Safety First.
Bryan-- just another satisfied customer...