Solar panels, how high should they be above the roof

i'm going to re do some of mine
2" on the front edge 3" in back
yes water run off , helps keep from making dirt puddles, when stationary water dries up

we don't get very many really good rains that wash the panels

get some "nutserts" aka Rivnuts and the tool for setting them to the panel
using a permanent nut on the panel for fastening to the bracket
makes it easy to loosen the bolt and clean under the panel
or add tilt bars