Hey man, yeah i basically did exactly the same thing as you only with more seeds. I had them on my windowsil and they where doing find but after a few weeks the started to become very noticable... So i moved them inside and brought a light. a set up in your atic would be fine only you'll need a decent light. They will be fine on your widnowsil for a little while provided its getting enough light and you make sure you dont over water ect..

You can see what mine turned into in my thread.. lol http://boards.cannabis.com/indoor-gr...eek-7-8-a.html