Hi there,
To use Google's in-house VPAID loader, simply use:
http://imasdk.googleapis.com/flash/sdkloader/vpaid1adsdk.swf?
followed by the actual ad tag (which would be derived from the Moat tag), for example:
adTagUrl=https%3a%2f%2fvast.brandads.net%2fvast%3fline_item%3d13723423&level1=GWK_TCA_DESKTOP&level2=GWK_BURST_TCA_$3&level3=burst&level4=preroll&slicer1=undefined&slicer2=undefined&pcode=vexigovpaid823483854014&spvb=1
Please note that the use of another VPAID loader might affect your statistics, and should only be used for debugging purposes to narrow down the origin of an issue.
Let us know if you have any questions!