I seen at least a dozen hacked up this way back in the seventies and eighties.
I would strongly suggest that you use a 'glass hood for this type of thing. Before that, I'd suggest doing a bit of air flow measuring and see that you will not get much air in, but will ruin some hard to find parts.

Here's an article
http://autospeed.com/cms/title_Ultimate-...10/article.html

I realise your stated goal is a little cold air, but as mentioned, removing the seal at the front of the hood will also allow cold air in.