The plastic inside the carpet seemed pretty flexible on mine (designed to be bendy I think) so that wasn't a problem. The screw tabs on the Bose housings were another matter - broke with a slight catch on the other carpeting. Had two screws holding each carpet panel (plus gunk and velcro) on each side. Need to also take the plastic trim running up the back of the door way off as well, then you can kind of rotate the carpet trim around and out after freeing the velcro etc.
First one took me about an hour to figure out - second was off in about 10 mins
This was quite useful but my carpet only had two screws.
http://www.zr1netregistry.com/frontspeaker.htm