I think he's probably guilty; however, the story of Scott at the bay was out from the begining and the media coverage was non-stop. If someone else had kidnapped Laci and was going to kill her at a later date, what better location to dump the body then in the bay where the husband said he was on the day of her disappearance. Afterall, the husband is always the first suspect in these cases.
The story that Scott had SAID he spent "the day" fishing in the Bay was out, yes. But nobody, and I mean nobody, knew what time the parking ticket for the marina had stamped on it. Nobody who talked about this case could do anything but go on what Scott said: "Okay, he says he left home at 9:30, so he must've gotten to Berkeley about 11:00..."
That was all the public had. Furthermore, there were doubts raised from the beginning--sometimes it appeared that most people doubted he had really gone to the Bay at all. It was by no means an accepted fact that he had even gone to the Bay.
And if the "story of Scott at the bay" was constantly being told, that works both ways: since the alleged involvement of the Bay was well-known, you can bet that if anyone had done anything suspicious in the ensuing days, such as dump a body, at the Bay, SOMEONE would have noticed.
Have you thought about contacting MG with your theory?
I don't think he's thrown this particular piece of crap up against the wall yet.