Once you've added the hooks and line tie, float test them. If they lie almost lever, with the tail slightly down but the back still mostly out of the water, they should work fine.
I would test one on the water before I finished all of them, to see if the weighting needs tweaking. I haven't made poppers that big, but I've made lots of topwaters that big and bigger.
The biggest poppers I make are 2 1/2", and they hang down at approx. 45 degrees.
The tail down in poppers is more exaggerated in small poppers, because they are light, and adding ballast helps them to cast better, but it's not required in larger poppers.
Line tie position is very critical. Play around with your test lure to see where to put it. I generally put the tie either dead center of the cupped face, or slightly above center, and then make sure my knot is all the way down toward the bottom of the line tie eye. That seems to be key to getting the bait to pop really well.