MinDevkit: Using Headers for complex objects?

Greetings,

I've built a cool object with MinDevkit with lots of functions, structs, and variables. The file is getting pretty unwieldy. I'd like to move a lot of this stuff to a separate header file, or ideally a few separate header files. So I can call my function inside the Message code, without loads and loads of preamble in the main object file.

But with min devkit, we are essentially declaring a class, not defining one. o basically what I'm trying to do is split a class declaration across multiple files. Which is not great C++ style as far as I understand it. I've tried a few different ways to hack this. Some things can be externalized and some things can't, and the number of exceptions I'm encountering wind up fragmenting the code in confusing ways, which undermines the reason for doing this in the first place.

Any C++ Wizards know of a good way to take the entire private members section of class declaration and put it into a different file from the rest of the class?

I'd love to keep my main object file focused on attributes and messages and keep the gobs of preamble those messages depend on somewhere else.

Thanks for any input!