Balance pins are good for static weight only, they will not show chassis or suspension tweaks. Likewise scales are influenced by spring preload and other suspension issues.
So, what I do is use balance pins when building kits and placing electronics and extra weight. After that I ussually just block 1 end and lift the other off the bench at the center an ensure both wheels clear at the same time. I have used scales but it has been when the car is tweaked and I just can't find the problem any other way....and it has always been a chassis plate or brace tweaked.
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