If the actual bowl outlet is horizontal, AND you could figure out some way to seal to that outlet, then I suppose it could be done. That takes care of the CAN IT BE DONE. The question you did not ask is, "Should it be done?" and for that the answer is a resounding NO. Once you remove the vertical component of the outlet, which the UniFit adapter provides, you change the toilet from a siphon bowl to a blowout toilet, and the tank has absolutely inadequate pressure to flush the toilet that way. So you would wind up with a toilet that was easy to install and flushes terribly. With no way to correct it.