The broker does charge debit interest for the margin requirements. This is the confusing part (at least with IB) as this margin requirement is not visible as a cash position. But is "eligible" for debit interest being charged to you by the broker.
So the foreign margin cash landed to me is eligible for the debit interest, but it's not clear whether I'm also getting FX-rate exposure on that cash ?
I see.. but for sure I'm not exposed to the exchange rate on the whole contract's notional, which means my P&L calculations are wrong, so back to coding

Thanks!