Redmadrona, Calyxa's tutorial is the only one I know about. After making another tile, what I do is: 1- hide ground plane 2- select the new tile, go to maximum zoom 3- move to the border and move the new tile until the match is perfect. Calyxa's suggestion about grouping the tiles, scaling the group up, adjusting borders and scaling group down works very nice. I have no visible gaps in my renders that way.