Well, there may be some shade on the edge if you have the light centered (which you should). Still, I don't know if it would be a lot. Then again, I've never done it so don't want to stick my neck out there saying everything will be ok!
How tall are you planning to make your hood? The higher up the lights are, the less of a chance there will be for any shadows. If you are a perfectionist like me, look for a 6' (or close) light!
And just because I mentioned hanging lights, doesn't mean you have to hang them (as Mr. Limpet said). You can have a top to the hood and screw it to that, or hang from the top of the hood, or if you are like me and don't want/need a top, you can build a little shelf along the sides and and rest it on there. Same will go for two 3' lights.