What I do is look at as many other tanks and pictures as you can until you are reasonably sure how you want it to look and then mask one side up by hand. When you are happy with it make a paper template of that side and transfer it to the other side.
One thing to be careful of is to make sure you have the same amount of chrome above and below the badges, they look lousy if the badge is too high or low in the chrome panel
You cant see both sides of the tank at the same time so a minor difference will not be noticed, as long as when you look down from the top it looks the same it will be ok.
These tanks were originally all hand painted so there is no absolute "correct" way.
