Attaching a strap on Dingbat case for soft case neck

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Has anyone somehow attached a strap to a Dingbat case that goes across the width, like Pedaltrain ones have, so you could slide it down a soft case's neck? I'm able to slide it down horizontally, but it sticks out to the sides, which can be a problem in places like the subway. Sliding down vertically would keep it really streamlined.

Thanks.