You know what? Because it's pinched at the top and is only seeing the proper pressure in a thin band rather than the more spread out correct size you're likely going to find that the seat post walks down the seat tube over time because it is only tight around the top and is too sloppy lower in the seat tube which allows it to move side to side a little. You'll be regularly having to loosen and lift it out a half inch or so when you notice that you're legs are getting more bent. And THAT is why the right size is needed.

Cutting a beer can shim and slipping it in between the seat post and shim would likely aid a lot in avoiding this. I know you don't believe this at the moment but after you have to re-adjust your seat post a couple of times think back to this.