Hello Erce,
I use PL lights, that are U-shaped fluorescent lights. This is what mine look like:
http://www.rainforest-frogs.nl/shop/images/Z0080.jpg
I could find it in 4000 Kelvin. I grow and flower my plants with 4000 K, haven't seen problems yet... and if you can give it day light I think you could come close to 5500 K on average.
FYI, 11 Watt is a bit shorter than 24 cm.
I also saw this type of PL:
http://www.rainforest-frogs.nl/shop/...JF-120x120.jpg but I have no idea in what colors it's available.
Sounds like a fun project!
Nicole
PS almost forgot to say welcome to OB!