How common are these to spawn and what can I do to encourage them to spawn?

I've only seen one spawn in 10+ hours of gameplay, travelling/exploring seemed to make no difference. If I'm simply missing the others maybe make them have a glow like the game lights to help spot them?

Edit: Nevermind you can change the settings in the mod options or directly in the control.lua file.

Where is the file that defines what the resources are? I'd like to remove the 1000 wood and reduce some of the values of the other crates.