I have never had a signature so I made one and practised it over and over to make sure it looked same or if not similar but when I did it on the passport it enbed up being really small does this matter?
I have had passports since I was a kid, been to many countries and being a crewmember you can imagine how much my passports have been used and how many immigration officers have seen it.
With all of that, I have never signed my passport, even though there is a space to do so. No one ever asked me why, not in the US nor Europe, not in the far or middle east.
However, a signature is a personal choice, being small or big does not mean it's bad or good. If you ever been asked, just say this is how you do it. Size does not matter in this specific case (unlike other things).