I worry that you're trying to be everything to everyone. Just because your backend can handle anything type of "shout", have you considered effectively turning it into a white label, and creating dedicated "sport" brand, etc.

If you manage to get X number of people to sign up, currently they likelihood of finding someone who wants the same thing is significantly lower than if those X people all signed up to looking for a similar thing.

Though I should imagine there is some advantage to keeping it generic to a point (sport over tennis) as someone may just be after someone to play games with, and might also be up for badminton or basketball or whatever.