With the adjustable flange in the top position, there is a huge gap between the adjustable flange (gray) and the trigger (black, in the hole).
And thus, you have to move the pedal quite a fair bit before actually reaching the mechanical trigger.
Even with the flange in the lowermost position, there is still a gab between the flange and the trigger.
I disassembled the flange and the bracket:
..And put the bracket back on - mounted on the underside of the pedal.
The screws are tricky - the best way would be to mount both screws the correct way, and add an extra nut to the frontmost screw (the threading is in the pedal itself).
As I did not have an extra nut with the correct threading, I put the frontmost screw upside down and tightened it by hand - as it was not tightened with a screwdriver (there was no room), it won't hold that much. But - I tightened the back screw (with nut) with a screwdriver and a spanner, and it is this screw that will keep the bracket affixed to the pedal.
But - now the flange (barely) touches the trigger, and any movement on the pedal will be registered by the trigger, instead of having a lot of dead room at the start of the pedal travel.
Issues/future improvements:
The bracket is barely scraping the front of the pedal casing, impeding free travel - I might unmount and slightly bend the bracket, to keep it from touching the inside of the pedal casing.
I'd like the bracket to be securely fastened to the pedal - I might locate a nut matching the threading and mount the front screw the right way, with the nut underneath. Or - using a smaller screw with matching nut, a screw that will go inside the threading on the pedal.
An alternative solution could be to do as evilcartman suggests - to just attach something to the flange as a spacer, craft foam, metal or whatever - filling the space, making direct contact with the trigger sensor.
For my pedal, the perfect thickness for such a spacer would be the thickness of the pedal + the thickness of the bracket - this the same distance the flange has moved after moving the bracket to the underside of the pedal.
Edit: I ended up moving the bracket - see my post on the next page.