Roddy? Shortened to Ro?

[luckiestgirlintheworld]

Due in August with DS2.
I really like the nick name Ro and am wondering what I could call DS that could legitimately be shortened to that. (I don't want to just call him Ro officially).

I really like rare names though, so I'm thinking Roman and Rowan are too common.
And really it wants to be a traditional English name to fit with his three brothers.

What do you think of Roddy? And could I get away with calling him Ro?

One of my criteria for name-selection was that I would like the most natural diminutive at least as much as the full name. To my slight disappointment, both DC insist on the original rather than the nickname. Make sure you like whichever long name you land on, because it won't always be your choice to make.