Back in the day when nobody ever wore seatbelts if you were coming to a hard stop, etc. it was courteous for the driver to throw out the arm belt. You know the one where your mom or dad would swing their arm out over the passenger seat and act like a virtual seat belt.
Kidding aside, I think what you will find is that the seat bolsters plus seat belt will do a pretty good job on their own. I suggest a couple 1g turns during a test drive to find out if this is a real issue.
You may be used to cars that have little to no seat bolsters and a higher center of gravity. For example, if I pull just a .25g turn in my minivan I can get everyone sliding all over the place in those large slippery leather bench like seats. This doesn't really happen in the Camaro unless you start pulling some Dukes of Hazzard jumps.