Is it possible to use an external spread spectrum clock for LT8361 (and LT8364) case?

Hello

LT8361 has provision for feeding in an external clock (MODE/SYNC pin), and also a pin to set a fixed frequency clock with a set resistor (RT pin). I would like to feed in a spread spectrum clock to the MODE/SYNC pin to try to spread noise out over a greater frequency range and I would like to know what should be done with the RT pin in this case as I cannot tell from the datasheet (see http://www.analog.com/media/en/technical-documentation/data-sheets/lt8361.pdf )

Same question for LT8364 (http://www.analog.com/media/en/technical-documentation/data-sheets/8364f.pdf )

I know that should be possible for LT8650S (http://www.analog.com/media/en/technical-documentation/data-sheets/lt8650s.pdf); see page 23. "A synchronizing signal that incorporates spread spectrum may reduce EMI."

I want to use LTC6909 to create various clocks with different phases but with spread spectrum (http://www.analog.com/media/en/technical-documentation/data-sheets/6909fa.pdf )

Please advise in this regard, or if I have missed something in the datasheet please let me know. 

Thanks!