Stella Sky was causing server side crashes, I suspect that it was doing so on the client as well for single player games too. I have reported the issue and removed the mod. It shouldn't cause any world corruption as it never owned any ID's.
I added my new mod TerraCart to the pack so that when you have your huge sky base up and running you can use the wooden rails from Extra Rails for cheap rails to get you around. Because when you right click any trick you will be in a minecart and when you exit that special minecart it will go away!
Updated some mods and brought a production server back online for this pack at us2.kreezcraft.com:25565