P&Y does vary in its measuring system on some occasions from B&C. For example, B&C will allow three circumferance measurements to be taken below the prong of an antelope and P&Y requires two above and two below, regardless of where the prong falls. There are minor differences on a few other animals as well.
As for velvet, the rule is (P&Y) that they recognize velvet entries for the one publishing of the hardback record book, which is printed every six years. After that, they are removed from the hardback book, but are still kept in an alltime file category in their records. In the hardback book to be published this spring, there will be a CD in the back of the book which will show all of those entries, but the older ones will not be in the printed text of the book.