The screenshot was edited by me in Paint so I'm sorry for poor editing but I hope you still get the idea.

I was about to ask for the option to remove the "Contains x stack(s)" tooltip line, but this works too.

All you should have to do is set contentHint to null, here:

I'm looking into adding a proper option to disable this entirely, though.

Adding a ci.cancel() to

The Contains x stack(s) can be removed by setting the tooltip type to None or Vanilla in the configuration.

Ah, I didn't know that. I found out that cancelling the drawing of vanilla tooltips when the item is a shulker breaks the mod's tooltip rendering since the mod modifies the drawing instead of adding it's own method that injects into drawing them.

I was about to ask for the option to remove the "Contains x stack(s)" tooltip line, but this works too.