Tramming the OrdishBot (née Cupcake). I’ve upgraded my bed from 100x100 to 200x200 (mm) and added some levellers. I’m now within ~.003" across the bed (and there’s a hump in the middle of my mirror). That’ll do.
+1 for the correct verb.
Try pinning your board in 3 places instead of 4 to create a plane. Unless your platform is too warped, it’ll deter that hump.