I say reserved slots are BS, some people don't even have a paypal account or any way to pay you, some people have an insanely hard time just trying to convince their Family Members to buy something online..If your going to do the reserved slot you should host using kalph's servers or someone elses so you can host 100 people, that way its impossible to have the server full of reserved slots.
Edit:But if that's how you run your servers I wont even bother telling you what to do, it just seem like a smart idea to me to use part of the money you get to upgrade your server to something like kalphiter's server hosting system.