If he had done what I posted above, he would not have to have faced public scrutiny. He could easily say that he chose not to tell others around him until the cat was outta the bag, otherwise it would compromise his efforts. Very easy to come up with a scenario like that and make it believable.
Truth be told, he probably would have gotten several positive interviews/stories on it in terms of "exactly" how did you do it, how close did he cut it between mats, etc...
Yes, he certainly could have said it was a joke, quite simply too. He gave away one big hint by saying that he runs for fun, that's a deal sealer right there.
He could have helped Race Directors in how to make it harder to stop those who don't want to run the whole course (think William Smarto and how he helped the banks). No, I'm not comparing him to a bank robber, hardly, but I'm saying look at the end result.
Now look at Kip Litton. Everyone and their brother knows what he did and how he did it, no big secret. Kip knew that he had full running attire changes during the race but just came up with something and then said "prove it didn't happen that way". He even sat down for an interview, even faced with overwhelming evidence, he didn't care. In the end, where is he now? His life went on and the thread about him has been gone for ages.
If I were Frank's neighbor, I would have had a heart to heart with him. Frank had other avenues to escape, but the internal and external pressures were too much for him to really think it thru. Pressure alters our thinking and again, he was a bright guy so you can imagine what was going thru his mind. To me it's sad all the way around.