Do you have any links to the hood and light your using? I am setting up a 20L right now and would love to have a carpeting plant. I prefr the look of a tank with alot of rock and driftwood but, yours looks great with the carpet.
Throw "Zoo Med AquaSun T5-HO Double Light Linear Fluorescent Hood, 30-Inch" into a web search and the fixture model I'm using will pop up. The bulb is "Zoo Med Flora Sun Plant Bulb T5 High Output 24 Watts, 22-Inch." I just have one bulb, but I'm ready to put another one in next to it since it can hold two - probably the 10,000K or "Ocean Sun" bulb. Maybe it will help the HC grow even more, but I'm getting it mainly for the aesthetic factor.
If you try the paperclip tactic with your new 20L let me know how it works. Good luck!