Now this is all new to me. Please bare with me on this as I am trying to understand.

So I show up to fly with my Vangaurd 6 channel FM system that I originally purchased on channel 42. When I arrive I see "Bob" is there and I know that he flys using channel 42. Okay that is fine, because when this issue came up I reviewed the club frequency list and ordered up three crystals sets that are either open or have limited use. If I have read this thread correctly it is illegal for me pull out a crystal set that corresponds with an open channel and swap the crystals in both the TX and RX at the field.

Is this exactly what this thread is saying?

I do not see anything wrong doing this. The transmitter still broadcasts on the 72 Mhz frequency all I have done is alter exactly where in that frequency the information is transmitted.