I've thought of a gap in the timeline.
For years fly rods came in a standard length / weight. For example 7' #4, 8.5' #5, 9' #6, 10' #7, 11' #8 and so on.
When did long and light start?
My only reference to long and light is Geoffrey Bucknall having his Brightwater rods made for him in one line weight (#3 I think) in 8', 9', 10' lengths. I had an 11' #5 Clan rod (wish I still had it :z19) but I hadn't come across anything lighter until more recently. I seem to remember that Bruce and Walker toyed with long and light but the angling press slated the rods and they disappeared pretty quick. Hexagraph went too but that's another story....
In my dealings with Greys (I got quite friendly when I had my bamboo made) they poo poo'd the idea of long and light saying no one would use them and they were a bitch to make. They now have an 11' #3 and a 10' #2 in their range!
So when did the technology catch up with anglers demands and give us long and light? To me that was one of the best things that tackle development gave birth to.