How to make interior cabine ?

Hi
i whanna make an interior cabine for my levasseur pl8
my question is if i make a cabine interior i have to do a copy of my fuselage and flip the poligon side or i have just to paint the interior whit 2 side painting ??? or other method ?
i whanna make an interior cabine for my levasseur pl8
my question is if i make a cabine interior i have to do a copy of my fuselage and flip the poligon side or i have just to paint the interior whit 2 side painting ??? or other method ?