Patrice, Good News!
With some help from the FreeBasic Forums We do not have to worry about @4 decorations any more.
In FB to suppress the decorations the solution is to enclose the whole BBProc in an Extern block like this:
Extern
Extern "Windows-MS"
'// The main exported plugin's function would be bbProc, like this:
FUNCTION BBProc (byref BBP AS BBPLUGIN) AS integer export
.....
End Function
End Extern