This simple measuring jig fits between the top of the z-motor mounting plate and the bottom of the x mounts. When it fits about the same on both sides you should be good to go! -Alternatively you could make two of these and lower your z until it bottoms out on both. Mine was designed for a Tronxy P802, but it should workable on a lot of I3 style printers.
My printer as it is setup up currently rarely needs any adjustment if the bed is well leveled once. I just do a quick 4 second check with the jig after homing and about 10% of the time I may need to turn a z motor a click or two. Good enough for me!
HOW TO USE:
Flip the model flat on its back. Then scale the length to your needs. It is 100mm long to be easy to scale. My setup happens to require 77MM. So I would scale in one dimension to 77%.