On our 2015 LE2 a 225X75X16 tire will not fit in our spare tire housing, so I installed a 225/75/15 Goodyear ST spare, same tire that Oliver now installs as standard. Oliver said the fiberglass tire housing on the 2015 LE2 a 225/75/15 tire would fit. My 2015 Ollie came with a 215/60/16 spare tire.
Here's some research done on spare tires:
As far as towing level, I'm starting at 23 1/4" from top of the ball, our TV settles about 2" with Ollie connected, the F350 rear end is still higher than the front with Ollie connected, with Ollie looking close to level. Our Ollie towing experience has been very stable with original 5200lb axles and original Dexter 5 leaf springs.