Adjusting seatbelt speed?

Any day now I'm waiting for the seat belt clip to go through the window of my tdci 90, it recoils so fast and I just keep forgetting to stop it! Is there a way of slowing it down? Plus I notice when you go over bumpy surfaces the damn lock keeps coming in too easily! Hit a bump and rather than just bouncing a little in the seat I just get my shoulder wrenched downwards instead! Any ideas? I'm assuming thier both on the same spring, can the tension be slackened off on it somewhere?
Thanks

i wouldnt mess with it ... but you could change it for another one (older model)

Fair point! I suppose seatbelts shouldn't be messed with, Good idea about the older one though! Thanks

yea ive learned the hard way not to mess with them unless there broken