This is a newbie question i know But, I just listed a new lawn and the grass is 18" tall now i've never really stopped to think and just cut when it's that tall. (take the trimmer to it first). but this is a new lawn and i don't want to have the grass get over stressed. i was thinking take the trimmer to it first i know but what would you do? cut it at 4.5"? or down to 3"? how would you go about this?