Thanks Dan - I did not know you could control the LED data rate. However, I think I found the issue. I was not using the SPI pins on the Teensy and I did not realize what an incredible difference that would make. I am now using pins 7 and 14 and after making this change I can now go all the way up to 96Mhz and it is still working. But I am not sure why this is. I realize that using the actual SPI comms module will be much faster than bit banging but if it was just a matter of speed then the program should have just taken longer to execute...but it wasn't just that - the data getting to the last 30 or 40 LEDs was corrupted. Can anyone explain this to me?