Honestly, I just keep it where it seems about right. When the bike is on the kickstand and I push up on the bottom of the chain, I can push it up a bit over 1/2". Once it gets over 3/4", I adjust the chain. Note that even when I stand the bike up, it's own weight make the butt sink (I have very low preload set) and checking it with it holding up it's own weight or with me, it is pretty tight. I'm due for a chain guide and have one laying here, but haven't swapped it yet. I have a total of 8,000 miles on the bike and about 3,000 of that was with the 12/43 combination. (I think I said 2,000 before, but he more I thought about it, I realized it was much longer than that because I didn't get my 13/48 installed until around 7,000 miles). Am I running it too tight? I don't know. I guess we'll see if it causes any issues, but so far, so good. The stock 43 tooth was starting to wear at 7,000 miles when I swapped it, but I could have run it for a fair amount of time longer I think. I think most people adjust the chain to about the right tension, but then wait too long for the next adjustment. Accelerated wear seems to occur during that "I'll get to it soon" period.