Speaking of waiting long, I just took the cake.

So I found a solution, and ferrite beads were my salvation.

So part of the delay was my finding a messy but stable way of putting the battery on my front rack for a time...and getting sick of fiddling with it....but the annoyance finally got me to try moving the battery back to the seatpost with the power cable running along the top-tube again. In the end, I was too chicken to try cutting open one of my cables, but between my own scavenging and a buddy of mine, I ended up with four ferrite beads.

Installing one bead at each end of the cable near the head and battery came up negative. The same occurred with doubling up the ferrite with two on each end. So for the heck of it, I placed three ferrites on the wire where it made its closest approach to the Sigma....and.....Speed, cadence, etc lights right up as if the lamp was turned off, even at full power. If that hadn't worked, my next step would have been to get larger ferrites, and do some wraps - I read something about that cubing the effectiveness per wrap.

So being that I'm an engineer, but not an engineer in THIS field of study, I have two theories as to what I just did.

A) Either the ferrite signal attenuation effect in the power cable itself wears off with distance, and ferrite proximity to the stretch of wire actually causing the jamming matters (how could this be?).

or

B) The ferrites are the wrong strength to really clean up the signal in the cables to the satisfaction of my computer, and the ferrite surrounding the wire in that area acts like a Faraday cage, one that knocks out all those harmonics, but does not block the low frequency signal from the cadence transmitter. I guess I could test this by wrapping the wire there in foil and see if I get the same effect. I find this the most likely.

Either way, I've gotten a really noisy multi-day endurance lamp to run with a fancy-pants wireless computer in a way that looks pretty clean, and that's success. The battery is cushioned and protected in a Timbuktu saddle bag, and the wire is about as intrusive as any of my brake or shifter cables - a lot nicer than running the dumb cable down the downtube, under the bottom bracket, and up the seat-tube using TWO extensions.

Really interested to know what some of the experts think I did though.....

So I'd like to thank everybody for the good tips and help with this. I looked at a lot of forum posts in trying to get this to work, and hopefully this thread becomes yet one more to help the next rider get their gear to get along.

For illustration, I'll post some pics.