The maximum throughput appears to be limited no matter what we do. To reach the maximum, hardware flow control is needed because the time it takes to send each buffer is variable. You cannot use a fixed delay because sometimes it is too slow, you could have sent it sooner. Other times it is too fast, and you lose data. The improvement gained by using CTS/RTS is only marginal. Maybe twice as fast or so. It's easier to use a conservative fixed delay. This number depends on external factors like internet usage in your neighborhood. Bummer!