I would do:
6 neons -6"
1 sunburst platy -2"
3 panda corys -7.5"
3 zebra danios -6"
That puts you at 21.5 which isn't the end of the world. Just keep in mind that if you're inch/gallon is off by a small amount like 1.5" the tank isn't going to spontaneously combust...
are there any corys that are a lil more colorful
We have a trio of peppered corys and although they are darker than pandas when the light hits them the right way they are a cool metallic turquoise color
Sorry forgot to add a link there for you
http
/www.liveaquaria.com/product/scateg.cfm?pCatId=1161and here's a pic of one of our peppered, the largest one is about 1.25 inches right now. Sorry they aren't the best quality but you can kind of see the metallic coloring.