Al,
I'm unsure if my method gives me the best possible result, but with the DSI3, I will take 40 or 50 x 1 sec exposures, let the meade software automatically stack them and use that as the image for further processing. I also adjust the threshold level for the software to accept an image to add to the stack, upto 80% value.
The dodgy images are just discarded automatically.
Seems to work, and the "noise" , as shown by the jagged line in your 5s exposure, is avoided.
Maybe I've just had some good luck with software selection
cheers
Mark