Provide 7 feet of walk up clearance under the roof for taller players. I'm 6'3" and I hate ducking under sharp edged eaves to read the info.
Three feet wide by two feet high would be the minimum usable area for a double sided DG exclusive use board with a Gable roof. Allows for 6 letter sized flyers/info sheets on one side and a course map poster on the other side.
Four to six feet wide by three feet tall may seem large but a poster sized course map, flyers, local course info and non DG flyers can fill it up quick.
Extremely windy areas will require Plexiglas doors unless you don't mind picking up wayward flyers from the adjacent tree line. You may consider putting the unchanging info such as course map, etc. on one side of the board with a permanent Plexiglas cover and use doors or leave the other side uncovered so players can add flyers.
I've heard that tarring the buried part of the posts up to 3 inches above the ground will improve the lifespan of the legs although I haven't tried that method yet.
Make sure you place some rocks or bricks inside the post holes near the front/back bottom and top of the holes while backfilling. A cross piece of rebar hammered through the post may help also. Many people tend to lean on the board while perusing the info.