Cannot create Grifball gamemode variant for Reach

I cannot figure out how to create my own grifballl variant for Halo Reach. I was able to add the grifball maps and gamemodes by going into the hopper_game_variants and hopper_map_variants and copying the griffball maps and gamemodes and pasting them into my mods folder.

When go into the custon games, load a gamemode and make a few changes and save it as a new gamemode, The newly created gamemode will not show up the next time I boot up MCC.

Is there a way to create your own gamemode variants from unique gamemodes like grifball?

The recent update now seems to allow you to make grifball gamemodes and they appear in the game when you boot the game up again.