Congradulations on your casting! That really must have been a great experience casting with the best casters in the country and, further, to be right there in the running with them.
There is no question that taped distances are always much shorter than "estimated" casting distances, but not because of being a 1/4" per foot off the lane center line. Your math is considerably off on that. If two casts are identical except for the 1/4" per foot error on the second, the second will tape out at 99.978 feet as measured along the center line. Squiggles are a different story though. Of course, if the cutoff is at 100 feet, then it does make a huge difference.
The first time I ever rolled out a 100' tape then walked back to my fly rod - I was shocked at how far away it really is. That psychological trauma ruined my casting and all I could think of was to cast harder - which never works.
I think it was a big mistake to eliminate distance competitions as an individual event at the Denver show, and identical to eliminating downhill racing in the Olympics as a separate event.
It's a shame that people like Dan's buddy Bill missed out on competitions that have been held for many years in this country. The only option now is to go to Europe - an option that most people cannot afford to do.