A little padding around the chest does not make an impact vest. Only a perfectly fitting vest will reliably protect you when you hit the water surface.
NKB used a double internal Velcro neoprene strap system that can be individually adjusted for a perfect fit. Once adjusted, the vest is easy to put on and take off by opening the strap at the lateral zip. Additional connection straps keep the vest firmly attached to the harness.
Once again NKB offer two versions of the Impact Vest: one for seat harnesses and one for waist harnesses (without protection in the harness area).