This is a valid question. I'll take a run at it...
The cornerstone of my shot-in-the-dark was the "repeated" idea from LE that the girls left that parking lot "in a car" with someone [sic. they trusted.] It is rare for LE to reveal something [to the public/via MSM] unsupported by any other known fact. By 200o, no human remains having turned up, the locked Oldsmobile crossed off the list - I wondered. If the car they left the parking lot in is crime scene #1, and they vanished for all practical purposes, by 6pm ~ then did LE turn the inner circle inside-out over vehicles? Because that is a very short period of time. I wondered, because the same people were investigating Carla Walker's murder - accepted by then as a "stranger abduction." That murder remains unsolved, though her case has everything you could want. I wondered if the police were handling the girls disappearance as a "stranger abduction." The last 6 years of my career I spent building hotels and restaurants in Las Vegas. People take cars out into the desert and set them on fire - daily. It buys time, but never truly destroys evidence. The Texas equivalent of that is dumping cars in bodies of water. It was December. The most convenient body of water is...so I asked. Is there any way to find out if everyone's car was followed up on, known of, and didn't go "missing" by any means in 1975? The other question was whether any searches, shoreline or otherwise, focused on bodies of water. A body of water will return its victims - even if you try to weigh them down. If they are in a 2,000 pound tomb - don't wait for Spring to help you out. I was lied to regarding the answers to those basic questions.
There was no "butler", so he didn't do it. I'm trying to get RA "un-stuck" from his bizarro conspiracy theory, so I set TT's car as "ground-zero" figuring that would be easy for Rusty to rule in or out. If the husband did it, he was alone - your sister had nothing to do with it, blah, blah, blah. That was in 2009. Five years later he decided to take that idea seriously, but not using the methodical "paper" approach. IMO he took a creative approach - a reasonable request that I had already discussed with LE, built support for, and burned it to the ground. FWPD have the details, the Austin ppl to contact. It will never be investigated because of all the things that came after. I can't help being disappointed. A stone that will remain unturned. The target was not a specific person or specific car. The goal was an exploration of information that could short-list and/or rule POI's in or out. That's the short version. The last four years have been hard.