My problem is that a portion of the Arduino core code makes an assumption with basically no way for me to change it. I can't even enlarge the buffer because that's defined in the arduino core as well (so if I change it for my copy it will still have the old value for everyone else who tries to use this project I'm working on.) I think I'm going to have to bypass the transmit buffer and allow for unbuffered sending to the USART through a secondary class. This will cause my code to have to wait while sending strings (70us per character at 115200 baud) but this is more manageable than hanging the code while it waits for a serial connection. That's just not right.