Looking at
from
https://terrylove.com/wc/unifit.htm it seems that the 12 inch Unifit adapter is made from the same pieces as the 10-inch, but that an extender is added.
And the 16 has 2 of those extenders.
It seems to me that if a toilet had clearances, Toto could offer an 18-inch rough in toilet.
It also seems to me that somebody could make a kit to make a 13.4 inc rough-in or whatever size from a 12. I suspect the glue cannot be defeated, but maybe an extender piece could be made that could be cut to length. Just idea.... It won't be me.
https://terrylove.com/wc/unifit.htm it seems that the 12 inch Unifit adapter is made from the same pieces as the 10-inch, but that an extender is added.
It seems to me that if a toilet had clearances, Toto could offer an 18-inch rough in toilet.
It also seems to me that somebody could make a kit to make a 13.4 inc rough-in or whatever size from a 12. I suspect the glue cannot be defeated, but maybe an extender piece could be made that could be cut to length. Just idea.... It won't be me.