Thanks for posting. I tend to use 2.5" squares a lot too.
I think it will be nice using the 16 patches in the middle in place of the bigger squares but I don't think you will get the "punch" that you get with the larger squares. The contrast is what is nice and the pattern is easy to see with the big squares and then the smaller.
But do it, post it, and then we can all see. It will be an interesting study in how small changes can change a pattern look.