Upper (shoulder) seatbelts - not tight?

[c4koh]

All,

I've read through the posts, and see that there is an inertia pendulum that should lock the seatbelts under rapid deceleration.

On my tests, and in other cars, often pulling quickly on the seatbelt will prove the lock, but on my ZR1 no amount of pulling it quickly does anything - for both driver and passenger...

I'd believe that this is as intended - wouldn't expect both to be bad...

So question is: is an elastic shoulder belt normal? And do I need real deceleration (rather than just pulling it sharply) to get the seat belt hold??

I'm not looking for cinching (this works fine, and as advertised), just the surety that the belt will stop... when it needs to!

Thanks

Steve