I just started a 30x30 grid and you can still see all of the grid, just not all the numbers. they move when you're onthe row, so you can see them anyway. The only hard one to see all of it is the 50x50.
If you find it too small, click the magnifing glass to cycle through 3 different views then move the puzzle around my using the wasd keys or clicking and dragging the 4 pointed star near the bottom right. I'm doing a 25x25 right now and can see everything, numbers for each row included.