The
PP conversion rules specifically state that the
TO can make exceptions for any reasonable conversion - so just make sure you clear it with the
TO first, and then it doesn't matter what your opponent does. Keep a regular version on hand (and painted) so if the
TO says no, you have an alternate model to use.
Here is an excerpt from the
PP conversion rules:
Model Conversion Rules
Playing with a uniquely individualized and painted force is one of the most rewarding aspects of the
hobby. Just as with information disclosure and sportsmanship, players are expected to be unambiguous
about model representation. The following rules must be adhered to when using converted models in
organized play. These rules are meant not to limit a player’s modeling options but rather to allow
creativity without generating an environment that could become confusing during game play. At his
discretion, an event organizer can make exceptions to these rules to approve any reasonable
conversion.
Probably a good idea would be to write (paint?) the models name on the front of the base - so if it is Beast '09, write Beast '09 on the front of the base so that there can be no doubt on the part of your opponent.