I posted a few pics of the bigger valve cut open valve seat. From the advice ive been given, this is about the maximum this valve seat can be cut, long as the cylinder temperatures are in the normal range. Nothing real hot. Ill most likely be running a gasoline and E85 blend, something like a 50/50 mix like E50, which will bring cylinder temps down below running normal gasoline.
Granted ive spent next to $2500 altogether over the years, just to be able to cut valve seats, but the tooling i have isnt purposed for cutting that much material out. The tooling is really only for bringing seats back and adding angles, but ive figured out how to use them beyond their purpose. It took some practice trial and error, but i got it! Each seat takes roughly 2hrs to cut. Making sure the depths are correct where the valve stem tip is at stock location.