I've just started using this forum so I may be wrong, but there does not seem to be a lot of interaction going on. I've also failed to see any settings for allowing notification to post responses. Would it be possible to update the forum software being used to allow for this?
An active user group would be a massive positive and I'm sure would increase sales enough to compensate any expense this might involve.
As an alternative, how about setting up a Facebook group instead?