@foone does it absolutely have to be one contiguous sheet, or could it be made up from individual tiles of smaller ones? Is this for some kind of planning purpose or do they need to be seamless for aesthetics? Thinking of the approach I took with my 3d printed pixels, I'd probably experiment with printing a ton of gridded pages in A4 while heading to the shops for foamboard and a decent guillotine - that way you could also precisely set/control the size of each square.