I used to use the Thor Quadrant under jersey foam protector, and it sucked. It barely reduced the pain associated with clumps of dirt hitting me, and I know that any wrecked would have ended badly. Basically, it was a waste of time putting that thing on (basically a spandex vest), and I am glad that I moved on. The pressure suit style protectors can be worn under jersey, as can the Thor Sentinel, and either would be a better choice. Most people that don't wear any roost protection (or the foam crap) are more concerned with style than injury, and everybody wrecks in time.