I'm planning on building a 20' to 23" retaining wall using green pressure treated wood. I've seen other designs but wondered if there were any concerns with my design. My plan is to put 4x4's into the ground about 18-24" deep on 4 foot centers. Then...using 3 rows of 2x8 (7.5 really) totalling 22.5" high.....but putting the 2x8's behind the 4x4's, thus exposing the 4x4's totally. To me this seems better for two reasons.....1) 4x4 is not exposed to the dirt, 2) 2x8's are supported by the 4x4's and not relying on any hardware to hoild them in place. Plus I think it would look better with the posts showing every 4 feet. Other plans I've seen seem to hid the posts. Thoughts? This is in SoCal where it never rains....and I plan on getting 10-20 years out of the wall.