Adding another Box Turtle?

[pnshmntMMA]

I have an Eastern Box Turtle (Terrapene carolina carolina) that is right about 2 years old. We rescued him/her as a hatchling. He is just a tad larger than a golf ball, and a voracious eater. I have kept large communal aquatic turtles with great success, but I'm down to just this guy right now. I keep feeling like I want to add another terrestrial type turtle to his habitat. I'm soon moving him from his small tub he's been in since we got him. I was curious what type things there are to be wary of when adding another turtle. I was planning on getting a turtle of the same size, and one that grows to be a similar size. I hear about worries of disease, is there a potential of fighting? I will not do ANYTHING to risk my little guy, so if this sounds iffy, I will just be happy to have him. My aquatics really got along for the most part because I always use enclosures that are overkill in size so they plenty of room explore and not be crammed up in each other's space all the time.

Thoughts?
Suggestions on other turtles that might work?

 

[pnshmntMMA]

Sorry mods, I dropped this in the wrong section. Thought I clicked on 'not so spineless wonders'.