You are getting 4% when actual rates is closer to benchmark of 9% for huge risk in RUB. Think about it this way, you are investing in a risky instrument and straightaway losing 5% per annum just by holding it.
Not exactly losing 5% per annum, making 4% instead of 9% on a risky investment which definitely needs timing and some fundamental catalyst( Trump election, end of recession ). I was not the only one doing this, a good part of the HF community was long ruble since Trump got elected. As I said, I am not a forex trader. What is your broker and what does it pay for holding cash rubles?
The IB cash sweep only applies to accounts with a balance over $100,000. If you have multiple accounts linked to an account with over $100k you will not get any interest if the linked accounts are below $100k. Fidelity also pays a comparable cash sweep as well without any restrictions as far as I know. Nothing nicer than being having a rising MRC paid to you by your broker - just like the good old days. For the purposes of crediting interest on either long settled cash balances or short stock collateral values, only accounts with Net Asset Value (NAV) exceeding USD 100,000 will be eligible to receive credit interest on long settled cash balances. https://www.interactivebrokers.com/en/index.php?f=interest&p=schedule