Yes- Lake Taupo is highly dependent on the Lake "turning over" properly to mix nutrients with some uniformity around the lake- can understand with what you say that this could vary around the lake.
Current catches in Taupo in last few months and even summer tend to indicate the fish caught deep in the lake were doing pretty good- with well conditioned fish. And our fish caught just the other day were all good conditioned fish so fingers crossed for a good run this winter!
The Rotoiti fish are lucky with such a huge smorgasboard of smelt - huge schools of smelt on the sounder again the other day - in fact we tend to hunt the edge of smelt schools just as much as looking for trout sign when we are jigging there.I never use bigger than size 10 - totally agree alot of the smelt are huge in comparison to a size 10 fly. Pat Swift has told me he does ok on a size 6-8 if fishing a moving fly on the drift -i havent though.
When Rotoiti closes in a couple months gives me a chance at the taupo rivers and mouths - looking forward to it.