I think the real reason a Tornado is SOMETIMES faster than most of the production 20's is the 10 foot beam. You can keep it powered up into a higher wind range than a boat that is only 8'6" wide. I don't know what the Olympic class weight for the T is but I would guess it's under the typical Inter 20 wt. of around 420#.

But, I think if you were to build up a custom I20 with 10' carbon beams, carbon boards and blades, lighten up what ever else you could to get it near the Tornado wt., it would be as fast or faster. The I 20 has very fat forward sections and a tall bow, you can really press it downwind very hard before you stuff it.