Unless the helmet light is a fairly tight spot with minimum spill, this does not work well on recumbent designs with the bottom bracket located higher than the seat bottom (the Bacchetta Giro 20 is a relatively moderate such design). This is because your pedaling feet are so brightly illuminated that they are by far the brightest thing in your forward visual field, thus effectively blotting out your forward vision. Recumbent bicyclists call this "foot flash" and is the reason that front lights on such high-racer recumbents (dual 26, dual 650c or dual 700c in particular) mount headlights either above, below or in front of the bottom bracket.

It is possible to use a helmet mounted light on such highracers, but it really must be a spot beam with very little spill. Unfortunately, it seems the OP's light does not have that narrow a beam.