Vince,
With no response yet, I'll chime in. And perhaps show my ignorance. But I have never heard of hollow coil-over springs. I do know there are hollow sway bars. Lighter is the advantage to them, but the washers welded to them to prevent left/right movement can serve as stress points and allow cracking to occur.
Can you provide more info on hollow coil springs? Never too old to learn something new ;-)
Larry