What part of the 20L are you drilling? I think I saw somewhere they temper the long sides.Went a little overkill tonight. Cut a hole in the top of the hex (against Tru-vu's recommendation) and added the Tidal 35. I wanted the filter pad and carbon, but the skimmer is a much better Nitrate extractor. Using the vacuum while drilling and cutting worked awesome.
In other news, I got my 20 long on sale at Petco and am planning out that build and livestock transfer. Going to take my time on that one, make sure I will be happy with it instead of making big changes after 2 months like I did with my current tank. Also going to use a larger substrate so my sand doesnt shift like the Arabian desert.