It's actually a multiple-layered combination field. Each layer has an increasing level of effective density and a narrower projection, with the widest and "softest" part of the multi-field facing the ship. Kind of like one of those highway collision stacks of exploding trash cans of filler - first just a few, then more and more. Except instea of crushing and exploding trash cans, the ship transfers its momentum into heat through the spread out, thickening-density layered fields. And for safety belts, the ship doesn't actually touch the inertia dampening fields - an anti-gravity bubble field does, so the actual inertia is transferred from the AG field to the ID fields.
:: shrug ::
Simple.