DFP : How do I display two 300x250 ads in a 640x480 zone?

I am new to Google DFP, and was wondering...

I created a 640x480 zone, but I currently don't have an ad to display in it.
AdSense fills it with a single 300x250 ad.

Is there any way I can display two 300x250 ads in that 640x480 zone?

Solution

The first problem might be that two 300x250 ads would not fit inside a 640x480 box... they would be too tall so only one will be loaded. This could be the issue, but I'm not sure that google would ever load two ads into a single larger adunit anyway... I don't think there is a way to do this with DFP without some extra coding on your part.

You basically need to have a call back on your 640x480 ad that fires if no matching ads are found and appends two new ad units into it and trys to load ads for them instead.

An easy way to get this call back going would be to use the plugin I made: jQuery DFP

Take a look at the bootstrap file to see how to use the callbacks... let me know if you need some example code!