You shouldn’t want to run it as “Rich as possible”. That excess fuel is just going to wash the oil off the pistons and could do damage. You want to slightly on the rich side, but not “as rich as possible”. Like the previous poster, you should have the idle mixture so that you get a 50 rpm rise just before cuttoff. I would strongly recommend you get someone to look things over (mixture, timing, prop low pitch stops, ect..) before you run it again, and especially before you fly it. Setting the idle mixture is pretty basic, being that you needed to ask shows that you might benefit from an experienced mechanic looking some things over. Don’t read this wrong, I’m glad that you posted the question and asked, that’s great! Lots of people build a plane but really could use a second set of eyes to look at things once that assembly of parts becomes an airplane.