Toilet Rough In - Too Little Space

[Nicholas TenBrink]

So far I've seen plenty of posts on Toilet Rough in and too much room, but what about too little room?
I've recently replaced the floor and the drywall in the bathroom and don't want to have to rip it up if i don't have to.

So I bought a 12" rough in toilet not knowing the different(noob). Went to install it and the toilet lower half went in fine but the tank hit the wall and wouldn't seat properly in the lower half.

Measured the rough in distance and it came in at 9" , the old toilet had already went into the dumpster and off to the landfill, so there is no turning back.

So now i'm curious, how much space does a 10" rough in toilet typically have behind the tank?
Would it be worth the shot of buying a 10" attempting the install and seeing where we end up?

OR will I need to suck it up, cut back into the floor, install a toilet flange with a kickback and just get it done?