I was going to try this mod, but then the 3 knob came out, and I kind of forgot about trying this one. However, from the thread you have a link to, there is this observation from Edward:
I tried the mod.
Subtle is a bit of an understatement. I can't hear a difference.
Has anyone did this mod and found it usefull and audible?
Also this comment from Muad'zin:
Found an old switch laying about and tried the mod. It seems to be a subtle difference, not enough to warrant retiring my Korg A3. Then again the DOD 440 was a subtle pedal to begin with. Still a keeper though.
However, after looking at your pics, the switch wiring looks a bit different than the diagram...but I seen what you have done, so while it looks different, I believe you do have it wired correctly...So at this point, I think it may just be different than what you were expecting based on the observations that others have posted?