I can't help you on that Tony, but I understand your annoyance.
However, I have learnt to live with it. My switch is directly in-line with my right knee and, with a toggle extension, is easy to toggle on and off to control the shift. I seldom get to play in the snow anymore, or the existing setting would be long ago changed.
If you watch the RPM and speed, you can anticipate when it is going to shift down and just toggle it off.
I liked the old (before electronics) system where the engine brake was independent of the tranny, but that day is long gone.
Let us know how your change works for you.
"LOVE and LOSS, are two of the greatest emotions one can experience. -- I went to school to learn about "WHAT GOES UP MUST COME DOWN" but I had to live my life to learn the lesson of: 'WITH LOVE THERE WILL BE SORROW'."
David Stewart. (after loosing my NAVIGATOR)