I'm just getting into customizing 4coder even though I've been using it practically from the beginning. So far it's been an awesome experience!
From my perspective as an aspiring handmade hero the API is masterfully realized and very friendly and intuitive to use! For instance, I wanted to get rid of full path names in search buffers and got that going surprisingly easily, having no prior knowledge about the customization layer.
You've basically achieved the impossible, which is making me feel like a programming god.