Well FP 400 has a lack of speed. And the grain is pretty big. Therefore Xtol 1+0 has my preference. Less grain but a tick less sharp. 8:30 minutes at 20C. When you want a full seperation of the (grey) test chart strips FP 400 in Xtol expose on E.I. 250. When you want to do 1+1 around 12 minutes is OK.
But to optimize your result you have to do your own experience in FP 400 development.
I don't mind the grain as long is it's even and consistent, I will try 1+1 12 mins. for a dozen rolls or so, and if that doesn't feel right I'll test your 1+0 8.30 mins. instead, and then I'll take it from there.