Each line on your level should be .005 per 10". to be with in a line should be good. I use levels that are .0005 per line in 10" to get the slates right one the money. sometimes you have to do what you can because the slates are not flat. Always start with the highest spot and bring everything else up to it. As far as pins go, I wish all slates had them. The pins should be snug. Just mke sure when you move one slate at the seam, to move the slate next to it the same so you do not pop the pins. The slate on the Diamond Pros are pinned and machined flat on each side. They are very nice to work with. What has happend with old tables are that some of the slates are miss matched. Pool rooms shut down and they tear down the tables they do not keep the slates together, so they are mismatched.
Cuebacca, I will be at Hard Times Sacramento this weekend for the tournament. Let me know if you are going to be there or you live close to see if I can help you out.