Hi folks,
I haven't followed the entire thread, but this one caught my eye, so I
apoligize if I'm stepping in the middle...

One thing to consider is that a thermocouple's output is directly related to
its temperature.  You may be able to relocate it so that it is in a hotter
part of the flame to increase the brightness of the LED.  Different areas of
the flame will be hotter than others.  You may even be able to test it with
a propane torch to determine the "sweet spot".  Have not needed to try it,
just food for thought.

Mark

>There are a couple or three basic ways to make that LED brighter -- 1) use
>a brighter LED; 2) increase the gain of the amplifier; 3) combine 1 and 2;
>4) install a thermocouple with greater output.  I'm not sure yet, but I
>have a notion that some people's thermocouples are putting out more than
>others --