In reality, I believe the fastest loaders were probably running at about 300 B/s (2400 baud) but that's just a guess from what I've observed.
You run into problems with frequency response before you run out of CPU speed. There were fast loaders that had to be slowed down because the duplicators couldn't cope with them.
You have to take into account what the tape is made of & the analogue to digital conversion in the C2N.
Writing a 1 bit audio sample to the tape at full speed would be kinda interesting. However I don't think the bit that you write gets put straight onto the tape, I believe there is some additional circuit in the C2N. IIRC the zero's and one's are modulated on the tape somehow, not just stored as is.
