The tuberculed fins feel markedly different from the same fins without tubercules.
One of the tested effects is a huge increase in angle of attack capability (up to 40 percent) and higher lift/lower drag with far better control in the pre stall zone. both of these effects are very noticeable, and overall the tuberculed fins feel much more precise and positive.
As far as drag reduction overall goes, it's hard to quantify when surfing, but they certainly feel at least as fast as those with conventional leading edges.
Where I'm going next with it is as follows: The tuberculed fins increase angle of attack capability, so one option is, instead of just accepting the higher angle of attack as a bonus, to make the fin thinner ( this would normally lower drag but reduce angle of attack capability) with the tubercules the fin can be made thinner for lower drag while maintaining the previous angle of attack range.
Also since the tubercules increase lift, they should allow a reduction in fin area.
so more thin in a matter of millimeters? interesting quirky novelty