I learned from the TS agent on the phone that Tradestation calculates interest on forex postions held overnight at 5pm everyday but he couldn't tell me which rates are applied, and it doesn't appear on their website. Anyone here knows more about this issue ? I'll definitely open a position if getting positive carry on eurchf for instance. Also do you know in which cases the "Futures overnight fees" are charged, and how much they come to ? With IB I think they only apply to traders using unbundled futures rates but there's not much information about them on the TS website, except that they may apply (forgot to ask this when talking to the agent, he might have been able to answer and waiting for his email)
They used to have their swap rates available. I think they have a history of what they were in connection with their data for back-trading. If you ask on their EasyLanguage forum, someone will help.
I still don't know about the swap rates but the overnight fee is 0.1 usd per contract per day. Besides I've given up for the moment to use Tradestation because their multicurrency account is far from convenient if one really plan to use several currencies. Might get back to them when I have USD available as I'm still curious about their products.