If you didnt know this to get your reserve slots working you must
goto game create page
then your server
click on files
look for for this %server:port%\admin\startup.txt and press edit
then add this line reservedSlotsList.aggressiveJoin true
add your guys to this %server:port%\admin\ReservedSlotsList.txt not just procon
Then click save down below and restart your server.
As you can this is the same setup as gamearena and they never had that line in the startup text either.
The slots stuff hasn't been added right now because we've had reports it isn't working. If it does work I'm happy to add it by default.