I own two 300CE's and instead of fussing with the seatbelt presenters and loose trim pieces I simply removed the fuse from that circuit. Only downside is the passenger side outside mirror adjustment motor is on the same circuit. To grab the seatbelt with the presenter disabled reach back with your hand just above the door sill. It's much easier without the seatbelt presenters, especially for a passenger unfamiliar with them.

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Fred Hoelzle