Barring the use of Pythygorean's Theroem, there is another simple way to know the exact position of a cube's corners. If you understand the layout of a region (256 meters x 256 meters) then all you have to know is the Center position of the cube and the size of the cube to know where it's corners are. You just add or subtract HALF the size of the cube, depending on which way you are going on the 0-256 grid layout. For example; if a 50 meter cube is at 128 x 128 on the region , then the corners must be at 103 x 103/103 x 153/153 x 103/ and 153x153 (minus or plus 25 from/to 128). This will only work if the cube is at 0, 90, 180, or 270 Degrees. There is also a way you can know exact corner positions even if the cube is rotated at an odd angle. First, mark the angle of the cube, turn the cube to 0, 90, 180, or 270 Degrees and then find what size it is. Use the first method i suggest to determine the location of the corners. Then use a smaller prim on top of the cube in that corner's position. Do all corners and then turn the cube back to it's original angle. When you get the position of the 4 smaller cubes you will have the position of the large cube's corners.