function! <SID>SetMainDefaults()

    " your default options
    set tabstop=4
    set shiftwidth=4
    set expandtab
   
endfunction

" apply defaults right now
call <SID>SetMainDefaults()

" initialize vimprj plugin
call vimprj#init()

" define a hook
function! g:vimprj#dHooks['SetDefaultOptions']['main_options'](dParams)
    call <SID>SetMainDefaults()
endfunction