If we shim a bowl, we pin the front of the bowl down to the floor.
I would rather the bowl touch in front, then be level.
Since the floor is not level, hopefully it's low in front, that puts more water in the bowl.
If you tighten the tank, it will touch the cradle. You may need to use the other arm to push the tank down.
If it's not centered, start over, placing the tank centered over the inlet on the bowl, and then start to tighten.
Once it has been placed on off off center, it wont pull itself back to center.