thanks Danny, that explains why i have not seen many aircraft with codes on, i bought Peterrs book back when i started collecting all the info i understand there is a new one coming out this month, i also recieved a lot of Vultee engineering drawings and the E&M manual, all this just to get the correct shape of the fuselage and engine cowling forward of the cockpit, sadly i had to get rid of all the paper stuff i collected when i moved house but by then the main work was done.