I just finished my aluminum fixture plate. It double as an enclosure to run flood cooling. It's fantastic. I got the 3/4 inch thick slab, made it about 3 inches more than the travels of the table. Surfaced as much as I could with a 3in flycutter to make the plate level with the head. Then I drilled holes 1/2 deep and tapped them. It was pinned in place so if I remove each hole will still lines up exactly where they were when I drilled them. I start in the middle of my travels each axis and drill from there with 1in spacing going both ways. So far so good. What I would do next time though is get tool aluminum, such as mic-60. Its dimensions are much more accurate and I've been told doesnt expand and contract with temperature as much as 6061 does. I use aluminum because its easy to mill and tap and works just fine for a hobbyists needs.