My understanding is that whilst you can buy carbon rail specific clamps, most vertical clamps will work just the same since the oval rails have the same width as round ones, just taller. So the 3T would work perfectly. But this is only my personal understanding of it. I'm quite often wrong.
This might be a daft question, but if a post takes round rails, does it need a different clamp for oval? If not, I have a 3T Doric.