I didn't go above the base grid size as I found it challenging enough for my taste. But now that you asked, I might just do that :D. I have to say I really liked the game design from perspective of playability, once you get the grasp of how things work.
Read the description again when you try bigger grids:) I was like "ok, I made it, I know how it works", but yesterday I got a challenge from a player (if you complete a pattern without hints you can get the challenge code and send it to friend so they will play the exact same layout but limited in time or moves based on your solution). I was devastated and spent almost a hour trying to solve that.