I was in a head on in a 1994 Miata as a passenger. I'm 5'11" and was sitting slouched in the seat at the time. We had just enough time to realize the accident was about to happen (We were sitting at a stop sign) before the impact. I don't remember the bag going off, I just remember the bag sitting in my lap and my knees having pushed the dash forward. Otherwise we were unscathed. The propellant and powder they packed into those bags in the 94's tastes horrible.
It was sortof an odd accident. We were waiting to get on the local 4 lane from a smaller road(Turning westbound, so across the eastbound lanes. The person opposite us, didn't look before crossing (old school Nissan Hardbody - Tiny Pickup), he hit a Ford Taurus headed eastbound at speed (65 ish). The Taurus ran into us, bounced off, flew across the concrete island and knocked a Ram 1500 off the turn lane and into the grass.
Lots of energy dissipated between the two moving cars and the two stopped ones. The driver of the truck was life-flighted, never heard what happened to him. The lady in the Taurus broke an ankle, and the two of us in the Miata walked away with just soreness the next day. Dude in the 1500, I'm not actually sure, I don't remember anything happening to him.
I went on to buy a Miata a few years later. They may be small, but they were/are well-built and handled that accident just fine.