Scope mounting is a little art mixed with a little science. I learned the first time from Larry Potterfield on youtube, the second time from Shep, the third time from Ryan Cleckner. Now I sorta blend all the methods and as long as it comes out reasonably well, let it ride. A plumb on a string will get your reticle level, buy not necessarily level with the gun. The levels on everything get it close, but even they have their limits. The deck of cards between the bottom of the scope and the top of the mount is also helpful, but again, is not fool-proof. I like to shoot the box and see just how level the reticle is, but there again, it's not guaranteed.
I'd venture to say there is no perfect method or perfect mounting, and if there was, it would be $$ to the point most of us couldn't afford it.
I'd venture to say there is no perfect method or perfect mounting, and if there was, it would be $$ to the point most of us couldn't afford it.