Clamboni,
I only weight a lure after it's assembled, because it acts differently assembled than when each section is separate.
I put in the hinges, pins, line tie, plastic tail, and hook hangers, and then float test it in a bucket of water. I hang egg sinkers or split shot from the tines of the trebles until I get the lure to sit in the water the way I think it should.
I just finished an on the lake test of a 7" floating 4 piece swimbait made of PVC instead of poplar, the hardwood I used to use.
I only put ballast in the first section, because when I put ballast in the third section via a weighted hook hanger, the lures still float, but only the head is actually above the water. They hang kind of tail down, not really sinking, but more a drooping tail kind of thing.
In hardwood baits of the same size and design, I have had to use the weighted hook hanger, and also ballast weight in the second section.
In this case, because the PVC is less buoyant than the wood, the tail section didn't need any additional weighting, other than the split ring and 1/0 hook hanging from the third section, to keep it from rolling.
I'm still learning about this material, and it's differences from wood.
I made some 5" punker type lures from it, and they walk the dog well, too, plus they cast like bullets! That's what I was hoping for when I made them from PVC, because hitting busting fish from distance is crucial here in SoCal on our heavily pressured lakes.
But, because they are heavier, they are a little more work to work, so to speak.
It's a trade off.