Don't use YPN! There are a ton of threads about why not to use Adsense or YPN on a proxy site. It's not worth it.
I actually called Yahoo Publisher the other day due to an account problem. Proxies are permitted, however, you cant serve ads on anything other than the main page. 2 emails and 2 phone calls, it was accepted =)
Always check with your rep before you do something like this, that is if it's YPN we are talking about. If it's Goggle, then better send ten emails and take the average response