This is my first build. I made a Mustang body out of pine wood and used my full scale Ibanez GSR200 neck and a Seymour Duncan Single Coil Quarter Pound as the pickup. No volume or tone pot. The pine is pretty thin (1.25") but it was free. There is a huge neck dive because the body weighs about a third as much as the neck. The pickguard is made out of acrylic plastic and I modeled it after the pickguard on my Bronco bass. I routed it large because in the future I might add split P-bass pickups and pots. It is currently unpainted, but I will paint the body light blue and the pickguard white. I am pleased with the sound, it is fairly bright.

That looks great, man! If the neck dive is a big problem, try putting some heavy scrap metal pieces (if you can find any) under the pickguard, in some extra space. Someone I know routed out space for a piece of lead he had, but 1.25" is a little thin for something like that. I love the choice of the Quarter Pounder, I have a pair of those in my jazz bass copy and I love the sound.
The neck dive isn't so bad, I can live with it for the moment. I did think about using metal pieces under the pickguard, or switching to a heavier bridge (which would probably improve sound too).