Looking for right wood

[jelfiser]

i'm just looking at various wood sellers for buyng materials for my 6 meters cheap boat i'm going to start building next week:see

http://boatdesign.net/forums/showthread.php?t=12496

so i chose for the skin 10 mm plywood okume .
i'm in truble for the compromise i have to reach for the scantlings...

http://www.boatdesign.net/gallery/showphoto.php/photo/5836/size/big/ppuser/14047

i have to make them cheaply
i was oriented to make 8 section of (12x2cm) from fir commonly used for house building , but also with a bit more i should use sweden pine or pine
plywood ,or always okume
what do you suggest to me ?
Francesco
italy