I totally understand about the tags being way to big!
I had actually posed a question a while back about why dont they make these tags in all sizes. Response was cost.
It also the reason that I had a seperate collar for Phoebes' other tags. I seriously thought she might do the head over tea kettle thing,

from being weighted down. So that collar just hung with our keys.
Btw this avid tag did not have a phone number on it. It just said avid microchip.
I did however find a dog a fews years back that had the microchip tag with a phone number, I called it and they said they would contact the owners. 4 days later they finally reached them, the owners had moved over a year prior and not updated their info. Owners called to report the dog missing.