The flat flywheel mikeP lightened for me had the edge cut down at an angle using a brake lathe. Same with my aluminum flywheel, not much material outside of the pressure plate bolt pattern.
We had a friend mill holes in a flat flywheel for our LH2.4 lemons car. Just drilled into the edge, but didn't cut all the way out to the face of the flywheel. thought it might be an issue cause the sensor wasn't perfectly centered over the holes, but it works fine. actually he might have used a mill table under the drill press because the flywheel was held vertical. regardless, it worked out.
We had a friend mill holes in a flat flywheel for our LH2.4 lemons car. Just drilled into the edge, but didn't cut all the way out to the face of the flywheel. thought it might be an issue cause the sensor wasn't perfectly centered over the holes, but it works fine. actually he might have used a mill table under the drill press because the flywheel was held vertical. regardless, it worked out.