Exiled, that's a worthy achievement!
By the numbers, you should be fine dropping up to 23 liters of volume, which puts you around 100 liters.
I have often told folks that the Speeed would change character, once you were on a small enough one, to surf it with one foot on the accelerator and one foot on the steering wheel. I believe that you would see a marked difference in performance, if you never had to move your feet.
I just measured the distance from handle to stomper on the 8'5... that would put me into a fixed stance (if I ever lose 20 kg)
If you are over 5'9, I would bet you could surf the 8'2 in a fixed stance.
Volume aside, you will be dropping 1.5 " in width.... that is something to think about.
Another option might be to change it up a bit and get an 8'4 Creek.
At 105 liters and 28.5" wide and a flatter deck, that should get be very comfortable for you.
The rail curve and nose make it an entirely different board, while keeping the same tail.
Your weight loss is worthy of a new board!
or you could go small and get a Genration SP25 - Sean Pointers new Sunova line!
7'11 x 28.5 at 105 liters
genration.com/collections/sup/products/sp25?variant=27852092375140