I remember a few years ago, I read/watched something where a magician stated that there is no such thing as 'hands that are too small.' However, logic dictates this has to be nonsense, as surely it is possible to have hands that are physically not able to conceal a playing card (mine are a good example!). If it was all just a matter of practice, then we would all be able to conceal a jumbo card with enough practice!!
That being said, I don't think it really matters if the cards stick out of your hand a bit. Much like using a thumb tip, no one should be staring straight at your hand when you're palming a card anyway, so provided you can conceal most of the card, you should be ok. Plus, the position of your hand in relation to the audience makes difference. For example, if the card is sticking out on the side with you little finger, but you hand is down by your side, no one is going to see it anyway.
I don't do a lot of palming, but I do use the Gamblers Cop a fair bit. Due to the position of the card, you can have nearly half the length of the card sticking out of your hand, but provided you drop your hand to your side, no one will see it. I know I've never been caught doing it.
In essence: don't worry about it. Just move your hand of the area of 'focus' and no one should see anything.
Rev