As promised, here is the build for my 20 gallon long fish tank and stand. This was two years ago, so updated photos with corals and fish will be uploaded soon =). Since then I've upgraded to a 29 gallon tank, but since they have the same exact footprint I was able to keep the stand. The new 29 gallon has overflows and a small 5 gallon sump.
I made the whole stand out of 1" thick dimensional pine lumber. For a small tank like this, that was all that was necessary and it's held up just fine.