Closed captions and Vimeo

As I said in a previous post I am just trying CC for the first time.

Using CEA-608 I had positioned some of the captions at the top to prevent them covering some lower thirds titles (like most TV shows), but it seems Vimeo strips out the positional information (and formatting) and does its own thing. I see they prefer WebVTT but their info page is lacking in detail.

Is there any way to preserve the positional information? Maybe through a 3rd party service/app? Or just accept what they do and work around it?