What's so difficult about making bubble flares? Besides, you make the flare in one operation instead of two.
I don't believe you can use a double flare in lieu of a bubble.
When I install a CPS, I use a shim made from thick paper (like a matchbook cover), folded over one vane of the HB, inserting it in the slots of the CPS. It's a snug fit, but gauratees the correct clearance before tightening the sensor down.
I fail to see what the 'drag' affect of the starter motor has on the ICM.
When I say ICM, I'm talking the whole assy; coils and base electronics.
Is the ICM grounded by the metallic base? If so, I could see how that might affect the ICM's operation, as that base/ brkt can get kinda cruddy.