Hi Phil,
the 75% Tsunami (named the
Vortex by yours truly) is a 43.25" span (40" effective lift span) version. I scaled this one for a 28 mm 300W outrunner.
I'm not familiar with the Scorpion you mention but if it puts out 425W, it would be a tad too powerful for the 75%. I suspect it is also a 35 mm can diameter which would make it hard to fit into the narrow nose.
But there's no problem, we can just scale the plan to suit your motor!
425W would pull a 3 lb Tsunami around nicely. A 48" span (82%) would probably be ideal if built to 48 oz. Here's the plan at that scale.
The spinner and wheels scale somewhere in between 1.75" and 2" in size - I would go with 2" and just modify the spinner ring and front formers slightly to suit.
Hope this helps,
David.
P.S. Did you get a Pico or UFO 66 built? There's now a UFO 77 as well that I had laser cut. 600W would do well on that puppy.