Finally got these mounted - inspired by Rayven:

Some jammers or slant Z bars would look to match the angles you have going on there.

👍

Firstly, these lights are designed to be mounted pointy end down, and I wanted pointy end up, so I drilled out the bracket rivets, removed the brackets and then siliconed the rivets back in.

For the lower light I took a block of aluminium a little wider than the mounting holes and shaped it for the angle of the forks - I have +4" forks so the angle is steeper than normal. Then drilled the block to match the mounting holes.

Two bolts go through the bottom of the fitting and two angled (filed) nuts under the head of the bolts "clamp" the fitting to the block, through the lower triple tree plate.

For the top light I used a handlebar riser and put the riser bolt straight through the back of the fitting - then just clamped the riser onto the handlebar.