I want the terrain in my Skylands map to be the same (or at least more similar to) what it would have been in the canceled Sky Dimension in the same seed. There are mods out there such as Better World Generation or Skylands Forge that give you this terrain. Most of these mods are stuck in 1.7.10 and I have concerns about downgrading my game, so hopefully someone else can do this.
If you happen to come across this post, and have one of those mods installed, please do the following:
Create a skylands world with the seed "7054886416251170592" without the quotes (how to do this depends on which mod you are using).
Generate a decent amount of terrain (about 2000 by 2000 blocks would be good).
Upload the world to a site like MediaFire (please make it a ZIP folder because I don't have a program to open RAR files) and give the link, otherwise I will not be able to download it!
However, if you don't want to install any mods, try messing around with the world customizer until you can get a Skylands-like world with about 50 blocks of height variation.
It appears that the easiest trick to get Sky Dimension-like terrain with customized is to change the Main Noise Scale X and Main Noise Scale Z settings (I set both to 160). If you delete everything below Y=64 in the preset I used, it will look a bit more like the Sky Dimension.