The modification you did is abit weird because its too near to the middle of the rotor, your brake pads are even touching the indicator of disc thickness. Also using Honda disc on a toyota creates another problem, because the middle hub clearance is bigger on a honda compared to toyota so you need an adapter to prevent vibrations.
Contact area for JDM Single pot and Twin pot is the same. Its just that twin pot got bigger disc originally so it can dissipate more heat. You could actually modify a single pot disc into a 2 pot caliper without much problem, thats what I am using now.
If you want to use the full 275mm, you need a 16 inch rim and an adapter to mount the caliper further out.