To me, there isn't any huge weak point directly under the car. It's a pretty solid unibody and has frame rails in the middle.

Having no rocker panels doesnt help as that is somewhat part of it's strength.

Also when you lift these cars off the ground you can open any door without a problem. All three that we've had don't body flex that much.

On older cars like the miata or fox body mustang, bracing is an absolute must.