Unrelated to your issue, but you should really not use the old mod loader anymore. Eventually this will cause you more issues when it inevitably becomes too outdated and broken by updates. I'm honestly surprised Cucumber's old mod has survived this long without causing major bugs.
You can find a guide for removing the old modloader
here under "If you used Dani's modloader". This mod already has counterparts that offer the same features in the new official mod loader,
PartEditor for editing individual parts and
Build Settings for the grid parameters.