My installer left my 8' Pro low in the center, and more so on one end than the other. After he left I purchased a Starrett level, and really wished i had it before he left to check up on him. He had one that he used, but really didn't like me looking over his shoulder, so I didn't get to see what he was seeing. In fact, he suggested setting the table up with shims instead of the wedges, as he didn't like to do it with the wedges. I had done my own tables in the past, just by rolling balls on the slate, and quite honestly, got a better level than he got with Diamonds leveling system. When I noticed the inward roll to the center, I went under to check the wedges. and about 2/3rds of them were all the way out, and not even touching the slate. Right or wrong, I'm not sure, but I slowly raised the center of the slate on mine till I got within apx 1 line on the level. Level was off over three marks in spots when I started. As I was worried about breaking the slate seam, I first tightened all the wedge screws by hand till they all touched the slate, then tightened the center wedges as needed 3 quarter turns at a time. I would do this every other day to slowly bring the slate to level. Doing it this way, I knew I wouldn't over shoot it, if the slate continued to move. Thankfully, seam didn't pop, and table is much more level now than the dealer left it. Those Starrett levels are really accurate. Diamond has a great youtube out there on leveling their tables, but I feel they really missed the ball on on the design of their leveling wedge adjustments, in that it's really difficult to back out some wedge adjustments, if needed. Some can easily be backed out, and some difficult, so I would suggest going slow in your raising process, if you try to do it yourself.