Middle name doesn’t flow with nickname

Re

I find out the gender next week and if we have a boy we want to name him Finnley Jack (last name starts with K). We’ll most likely call him Finn a majority of the time. But I think Finn Jack sounds weird. Does it matter if the nickname and middle name don’t flow smoothly? If we’re every calling him by first and middle name (the classic “you’re in trouble” situation) we would use Finnley and not Finn. Thoughts?