the one shown in the picture is holding a 2008 Yamaha Waverunner (4 stroke)... those aren't lightweight, i think they're about 800lbs and as mentioned it on a boat that i run offshore and sometimes up to 23kts. lots of loads! the deck is flat so no issue, it is not directly secured to the deck to be easily stored when the Jet Ski is launched so we can pull reclining chairs. The PWC is obvioulsy strapped down to folding eyes. when running offshore the craddle is tied to existing eyes so that it doesn't shift from under the jetski
the one on my boat is currently holding the cat boat which is fairly light but it used to hold my hober, a 13' HEAVILY built hard hull tender with a 40hp evinrude, battery, fuel, etc.. that's about 1000lbs. I put some starboard spacers between the deck and the base board to make up for the curve. It is secured thru the deck with backing plated underneath.