Sorry, I may have misspoke. I didn't mean floating in the air, I meant force supports etc so by 3mm above the bed everything should be level and flat and start printing the actual model there. I guess I can model my own supports externally?
We have the bed close to level by shimming under the flexible sheet, but I don't think we will get it glass smooth flat and level.
If the two halved didn't have to exactly mate, it wouldn't matter. We use it for other prints all the time and are very happy with it. We assumed it to be level until we did this print and were surprised to see they would not mate.