Originally posted by def
Can't speak for other firms or about bonds for margin. Howver, IB has a unique feature that allows you to use one currency as margin for both. Ie. if funded in USD IB will use the USD to cover euro margin. Profits/losses would remain in euros for you to convert back as you please. When an account becomes flat, your cash would revert back to the base currency. Thus you could theoretically trade ESX or DAX in the AM and swap over to E-minis in the PM using the same capital.
