I think under is the universally approved method, presumably to "catch" the failed hitch as it drops.
You need longer chains if you need to drape them over the top.
I could be wrong, someone with more knowledge than me will no doubt have more information.
You could use some of those threaded link extenders like shown in the photo to give you a bit more slack.
2018 Ram 2500 Tradesman, CTD/CC/SB/4X4/Equalizer WDH
2019 Forest River Surveyor Legend 19BHLE