SV flywheel rotor lightening

Hi, one for the techies here... I'm interested in lightening the rotor flywheel on my K5 race bike here in Ireland as done by Spears Enterprises in the US. A friend of a friend has a lathe and a method of balancing the flywheel. Anyway, here's the problem...

I'm unable to attach pictures so here goes: there are raised lugs and a small countersunk 'dimple' on the outside of the flywheel. The crank position sensor incorporates two pick-ups, both with their own separate wire(s), one a single vertical metal bar which reads the lugs and the second twin horizontal bars which presumably reads the dimple. It has been suggested to me that the dimple is for balance but, as the lightening involves machining the flywheel back to the lugs and no more dimple, I need to find out what this second pick-up is for. Any gurus out there can shed the light?