We've added the support of custom sizes for the preflight editor. That means that on the service page in the calculator the user can set up the size of the item, see the final cost, and then go to the editor and upload their layout.
The editor, in turn, checks the match of the real size of the layout with those set up in the calculator. Also, the set-up sizes can be changed right in the editor, after which the price of the order will be recalculated automatically.