Best gap between fan & radiator?

I have started the process/experiment of making my fiberglass fan shroud. Lots of 3 steps forward, 2 steps back... or maybe it's one step forward and 2 steps back.
Anyhow, I have the first coat of resin on it today...
I have taken lots of notes and pics. If I am successful with it I will post the how-to.
One thing I have found out for sure, label everything!!! R-L, "up" and fan side, radiator side. You can see in the pic, not only is the wood scrap labeled R & up, but the cardboard it is on top up is also labeled R and "up".
C