The T-pipe PVC
pics look like Durso standpipe, which is a nice design because its so quiet. My tank is drilled, and surface skimmer design was much too loud - I always heard the sound of water getting sucked out. This makes me wonder if the self levelling siphon would be loud. (Durso standpipe has a small hole at the top of the T, so only a little air escapes, and is very quiet.) Here's the thread that was quoted from the krib - http://www.thekrib.com/Filters/overflow-skimmer.html
Andros, following rule of thumb stated earlier, figure 15-20g minimum for your 50g. How simple are you looking for? Baffle design is sweet because your controlling water flow allows for a very sophiticated filter. Wet/dry design doesn't need baffles and is very easy to build, if you want wet/dry (you wouldn't if you're injecting CO2
into your tank). A sump can just be a reservoir of water and nothing else if you want it to be.