Cook the macaroni in a large pot of boiling salted water until just tender.
Drain well and return the macaroni to the pot.
Melt 6 tablespoons of butter in a small saucepan.
Pour the melted butter over the macaroni and stir to coat evenly.
In a large bowl, combine all the shredded cheeses.
Add 1 1/2 cups of the cheese mixture to the macaroni along with the half-and-half and cubed Velveeta.
Beat the eggs in a separate bowl and mix them into the macaroni along with the seasoning salt and pepper.
Stir in the seafood mix, making sure everything is well combined.
Transfer the macaroni mixture to a greased 2-quart baking dish.
Sprinkle the remaining cheese and 2 tablespoons of butter on top.
Bake at 350°F for about 35-40 minutes, then broil for a few minutes for a golden crust.