Thanks for all the great suggestions. Looks like I have the Etherkit library version 2.01 so I updated to 2.10. This makes a noticeable improvement to around 2.5ms but I can't duplicate Don's results of 735us. I don't understand how our results could vary so widely. Could it be frequency dependent? I am switching back and forth between 7.030Mhz and 11.946Mhz.
So then I followed one of Jerry's (KE7ER) suggestions and modified my sketch to use his?si5351bx code. That was really easy to do and?si5351bx_setfreq()?took about 2ms to execute. Not bad - at 30WPM that is about 5% of the morse element length.?
Here is an ADDED BONUS.... I think Jerry wrote that code to save code space and wow did it ever. Using his code instead of the Si5351 library cut my code size from 22.4K (72%) down to 12.4K (40%). That is awesome! Thank you Jerry!! Even if I eventually decide to use two outputs for this I will stay with the si5351bx code for the code size reduction.
73, Jerry, W0PWE
