Here's the IDBF's document regarding paddle dimensions:
http://idbf.org/documents/watersafety/Boat&PadManufSchemes08.pdfDepends on the festival. When we went to Hong Kong last year, some of the Chinese teams had paddles that didn't have the IDBF stamp, so they had a sort of paddle mold in which they placed each paddle to see if it was the exact dimensions. Paddles that did have the stamp were exempt from this check.