I have the Beamshots with my Canon PowerShot S100 made.
The white balance is set to daylight.
aperture 2.0
exposure time 4 and 2 seconds
In direct comparison is always the same setting.
A ponit and shoot camera is not going to be able to accurately capture beamshots, you need a dslr, everything set to manual. P&S cameras are so limited, by design.
Try using the Tungsten WB setting while capturing beamshots. If you can custom set your WB that'll be great, if not use the presets to see which suits best.
Your technique is flawless, you have the creativity side down pat. The technical side you can only do so much with what you have.
Wb presets add a color cast to the final image. Each WB presets add a different tone.
Daylight WB setting will add a cast over the image, thats what WB presets do, each add a different colour cast.
With daylight WB, the camera assumes your outside in the sun, because the sun is reflecting the sky the final image is going to be cool, so the daylight setting adds a warm tone, final image ends with a warmer richer tone.
Try manual mode rather than Aperture. While you can lock your aperture in, the same can't be said with your shutter speed, it will fluctuate...ie won't remain constant.
With beamshots, you have to use manual so it can be reproduced accurately.
I noticed in your other threads, I saw a lot of over exposed beamshot images, particularly in the Zebralight thread.