Take a look at this screen capture of Notepad++ and the Meinit.xml file.
So what I did, was add a line under <Units>-<CarComplex>
Just follow the same syntax as the other lines. When choosing a CLSID, do a search to make sure there is not conflict.
As you can see, I named mine Test1. Under Test1, is the list of units in it. Look at the other entries and follow the syntax. To figure out what CLSID and name to use for the units you wish to add, look under <Units>-<Cars>.
Then you need to add the complex unit, to the country you wish it to be for. Look at my screen capture to see how I did that.
Its all very simple.
PS. I have tried many ways to try and get a complex unit with static object, no go. Also ships are a no go. The only thing that I could get to work was normal ground units. So anything thats under <Units>-<Cars> that isnt categorized as a Static Object.