On our servers due to Mystcraft and RF Tools dimensions being really unfriendly to performance we have opted to disable world creation with these mods and enable our own custom setup.
We are currently using the Multiverse plugin to create personal worlds for players that want them.
In order to get a personal world you must use the reward store on the website and purchase it with your website points.
There is a selection of different world sizes for you to choose from.
Basically what this means for ex. personal world "500". The 500 is the world border radius of that world.
So when its created this is set and you should have a circular border on your world with a radius of 500 from the 0,0 coordinates
Also available in the reward store is the ability to disable the weather and daylight cycle in your world.
This can also be added at the time of purchase as well in the options.
/myworld - Teleports you to the spawnpoint of your personal world
/addtomyworld (Name) - Add the specified player to have permissions to build in your world
/removefrommyworld (Name) - Remove the specified player from build permissions to your world
Note: With personal worlds its possible for any biome to spawn in it (Including biomes from Twilight Forest and other mods)
Also Note: If you are logged off from the server for more then 1 week it's likely for your world to get archived to save on disk space and performance. If you come back to the server and this has happened to your world you must either log a ticket in game and/or post on our forums to have it unarchived.