Currently, Wix forum doesn't support full-size experience and also a way that you can put your advertisements on a alternative columns in it. For example, I want to put the advertisements on a bar that is on the right or left hand side of the forum instead of adding them directly into the forum posts. In addition, we can't use them in outer area of the page grid. Most users don't view the advertisements when we put on them there. By this reason, we lost hundreds of dollars.
The reason why I want you to enlarge the forum was mentioned above. To use the ads ,and by the way, to use anything we want on forum pages, we will need to use more useful spaces. It has been a big trouble to us for a long time.
Thank you for your interest, I wish it will be fixed as quick as possible.