Here is a frequently asked question I think bears answering here.
"When choosing a crystal skull does the old philosophy that bigger is better apply? If a small skull is chosen instead of a large skull - is the energy or properties less?"
I am happy to give you my opinion about this. :-D
This is all about energy, and that isn't physical.
So the short answer is no, size is not what matters.
So how do you pick the 'right' stone?
What matters is your interest in or strong attraction to that particular stone.
You will be attracted to something that is energetically compatible.
IF you pick by size alone you may end up with an expensive paperweight.
I always think that if you find yourself coming back to one particular item over and over, then that's the one. No matter how small it is.
It's not the size that matters...it's what you do with it!
I hope that was a bit helpful.