ajkenne gives excellent advise. Unpinning the bottom and bolting it back without the wedge while taping the top tightly together will get a more accurate job.
Most scales have taper going down to the pivot end. Some compensation will be required if that is the case. Always a bit of 'eyeball' required to get them even.

So how much do those scales weigh?
They look big for most Bokers..

It might behoove you to send it all to a pro, FME.