Stop in for a cup of coffee

Wow, I have never seen one with that big of lines.. Im relating it to hydronic piping, that I deal with at work.
I would never run a 1" pipe and then up size to a 2", then reduce to a 1" again.. just poor practice, would it work yes. Although, its not optimal, you have good velocity and pressure and then open up to a larger size and loose it, however its reducing again and being forced back to that smaller size. It will work, but I dont know if over time it will cause any issues or will work just fine, it could be hard on the pump as well.. Myself I would look for a 3/8" inlet outlet, but thats just me.. Not to mention is it going to look odd making that transition from 3/8" to 5/8" where ever your going to mount it?
Going from the small lines into the bigger ones of the cooling radiator will slow the flow resulting in more time for heat exchange thereby making the returning fluid substantially cooler.

A similar thing happens with more core radiators.