Nobody's deck and hull fit perfectly especially after glassing the inside and outside of the deck and hull. Just remember to put some forms or spreader pieces in the hull after glassing so it doesn't close up on you. When you glass the outside of both halves, the shear edge will have glass that hangs over the edge and epoxy there too. You will never have a clean edge. So, that shear edge has to be cleaned up anyhow. Most builders glass the inside first because you can tape the two halves together. You will be surprised how much pressure you can put on that fiberglass tape by pulling on it as you tape. EVERY ONES' BOAT GETS DISTORTED A BIT AND HAS TO BE FORCED IN SPOTS. Make sure your glass hull is washed with water from blush so the fiberglass packing tape sticks well.

You can check out my interior taping method here if you want.

http://www.outer-island.com/Attaching_Deck.html