i've made cradles both for my heavy 13' tender and also for a waverunner on the boat i run using starboard. easy to built, no corrosion and a lot less expensive.
the triangles holding the supports are cut from the base and assembly is with SS screws (screws hold very well in SB)
picture was taken during assembly, additional supports on the inside are missing on the pics, one at each end
no water issues, the base isn't sealed to the deck so water goes out under the base. This one, for the Jetski, is removable so that we can use the top deck when the jetski and tenders are in the water.
PS Sky, as a midwesterner you are thinking of Palmer Johnson. The boat he captains is a Johnson.