Yes you can use it.
The precedent was set by my C130 in the vintage shoots. The contest organiser asked the committee if multi pump was admissable and the reply was that most people could see no advantage in multi over single pump. In fact it was thought to be the other way round if anything.
Just remember that this is an untried pistol and it may not be good for anything except plinking.
I have asked the rep to come to the UBC meet but so far no reply.

Regards
Jim