Gentlemen, take a look below at a 1/4 scale Bleriot. Could you conclude that the difference in strength between spruce and pine would have any bearing whatever on its success? I hardly think we would be looking a lot lot of spar snapping high G maneuvers that would depend on the marginal difference in strength of wood species to keep the plane together. Use whatever decent wood you can get your hands on.
http://www.geocities.com/Pipeline/Ridge/2450/model.htm