As a broader procedural point, i think this will be received quite poorly if you haven't established some relationship w/ these people that makes them want to listen to you.
Also, the thing about collars is different when you have a spotter. If it collapses on your chest all he has to do is go to one side and tip the bar to the side. If he's not strong enough to get the bar off of you that way by tipping it over and then squatting under the high end to pick that up even further, once it's tipped over he can take off the collar on the high side and pull off some plates until he can squat the high end off of you. Either way, that's better than the uncollared case which would have flying bars and weights.