There is also a cap. If you are at the maximum using 1 ad then you can't increase your weight by adding more.
The cap is applied BEFORE the number of ads are taken into account, so 2 ads will ALWAYS give more weight than 1.
I did the same thing last night. Changed all 1 ads on my site to a 5 ad. Still no change in weight. So, I'm glad I found this thread, this encourages me. But it says "Ads appear to be live on your site (as of 2005-02-27)." So it seems my pages need to revalidate? it's March 3rd.
Add your Google API key to your account through "account settings", then you can revalidate yourself whenever you wish.
Well, whoever revalidated my website thank you. It's now showing the correct weight and all my pages were there. As far as the API, I'm still working on that. It just throws me back to the sign-in page. I'm studying the API forum.