New Modbusmq project: Testers needed!

I have been testing the library and everything seems to work for what I use it.

Changing SPI communication speed with WIZ5100
If I understood everything well, then this should be the function tto be used. "setClockDivider(uint08 rate)"

Does anybody know where in the program I should write this function to change the SPI communication speed with the WIZ5100? I have tried some places like in setup and I do not see any noticable difference with my modbuspoll software.