My friends run our own private tournament every year in our hotel lobby.   It is a very popular game, but we use our own modifications to it....   Think playing King of Tokyo with the actual movie monsters instead of the copyright friendly ones in the actual game.   Its not that game, but that is the vibe...   We use the official game with the official  rules, but we use a different skin.

While playing our tournament in the hotel lobby, we usually get a small crowd who wants to join.   Depending on how early in the tournament they ask, we usually make room.   We have a trophy and plaque and its a fun experience.

we were talking about making it a GenCon Tournament Event, but was wondering if a modified game was allowed.  I tried getting permission from the company/designers for it, but they are too big to even notice my request.  

We are not charging for the event (beyond the base $2 charge), we are just looking to spread the enjoyment of a fun modification to a great game...

Thanks for your insight

As per the hosting guide, as long as you say it’s a varent and put the changes in the short or long description it should be fine.  But most importantly read the hosting guide.