Well guys it's been awhile. I just ordered Hiwin 25 series for the Z axis. I had the 20 series and decided that may not be beefy enough. I checked the Haas mini mill and they use 30 series but I could not use those unless I did some major modding to the Z casting. I think I can sneak the heavy duty 25 series in without any or very minor dove tail trimming. If I have to trim a bit I'm going to use a router with an end mill and a Harbor freight variable speed to get the RPMs down to a controllable level. I'm still going to use the 20 series in the X and Y. I also may cut the X down about a foot. I think 24" X and a 12" Y would be the perfect setup. I'm also going to draw up a square tube reinforcing frame to help with the Z rigidity. I know this seems a bit much but it works great as it is but I believe it can be better.