Hey Garuf, I personally think you DO need a good bit of planting space behind the wood, If you want to get that Amano "stem bush" look you need to plant the stems deeply.
Check out this ADA tank
http://www.aquatic-gardeners.org/stemplants.html, the foreground is relatively small but planted with nice bright glosso, sand would have a similar effect. Looks like a clearing in a forest, you need the depth of stems to trim them so they slope in to the "clearing".
Moss on wood or leave it bare with the bolbitis?
Looking forward to seeing your ideas come to fruition, Tom