Version Information

Minecraft version: 1.2.2
Forge version: forge-1.12.2-14.23.5.2859
Other mods (if applicable):

Steps to reproduce:

1. Start a forge servers, then add the mod to mods file
2. Join to server
3. Start to build vertically

Expected Behavior: No 256 limit

Actual Behavior: 256 limit

Comment: I just wanna build big skycrapper with my friends, but there's just cubic chunks rendering, with 256 blocks limit

Please read the Creating Cubic Chunks world section on curseforge page:

(actually just realized it's slightly outdated - it needs to be set to NEW_WORLD, not true - comments in the file explain it)