Do you invest, advise or other ways involved with any co.s that choose not to participate in YC or have matured beyond a YC stage? Some startups need more your sage advice, than any investment.
If I was in your situation and my startup closely aligned with pg's interests what I'd do is find a mutual contact who pg trusts and will give you a rave introduction.
For that matter the same applies to any other investor.
Honestly you are probably better off doing YC around when you'd do a Series A, or even slightly after, assuming all your investors would be ok with it (they should be), vs. really early.
