More thinking out loud.
If you kill two or three girls on land and they're found scant days after you pitch them or their parts on the side of the road, you have
to conclude disposal is the weakest part of your murder game. Its also unnerving having them found close to home. I'm wondering if Bittrolff moved his preferred murder site further away from his home to a more central location on the Island. It had to be close enough to his home and therefore his work, but far enough away to establish a new crime scene area - which solves his logistical problems with the killing and dumping.
Having shifted the place where his time consuming killing was taking place, he naturally shifted his dumping ground. So, he moves his preferred kill site to be more equidistant from his home/work site - let's say its around the middle of Long Island close to the shore. Let's say, its in Islip, close to where he has access to a docked pleasure craft - a sport fisherman's boat. Transporting a body would be less difficult, actually a shorter route, and it leaves him access to both the shores of Fire Island and Jones Beach. He's basically solved the problem of bodies being found close to home shortly after the dump, and he's relocated to a place where he can still make good time getting back to his home/workplace without arousing too much suspicion about his absence. He's also far enough away to be able to say he's gone hunting upstate while remaining close enough to enjoy his murder environment.
Our murderer isn't sawing up bodies in his wife's nice bathroom, or the house where his kids are running in and out, or the house he's running a business from. His murders are time consuming events. He's got to get the girl alive, bash her brains in and/or strangle her, and bring her where he can take time doing what can only be an extremely messy process - cutting her up. I would venture to say this fellow has hunted and dressed deer. He's got the skill of a butcher or a surgeon. He knows where the joints are and where to cut for easy removal. If he's a complete idiot, he's toting his saws and blades around with him. If he's smart, he's keeping his favorite dismemberment equipment at his kill site.
The cops should be looking for storage units of some kind preferably around the shoreline from Lindenhust to East Islip and close to a marina or private dock.
By the way, if your craft is large enough and you take a few full gas cans extra, Atlantic City is just a few hours away via the sea - no highway and no cops. You can leave for New Jersey in the morning, hop off your boat at Atlantic City, rent a car, have a kill spree, return to your boat and be home for breakfast on Long Island the next morning.
What do you think?