Custom Game Inconvinences

So I love to play with friends and sometimes its more than 5 people, so we sometimes play 3v3 howling abyss with all randoms, but the one problem is, once we get 5 people in the custom game, the game wont let us invite the last person unless one person either leaves and gets invited with the 6th man, or goes into spectator mode. Although u can still play with 6 or more people, it is just really inconvenient.