I own a Dolphin and have been wrestling with the idea of welding on a hitch in order to hold my big 2" bike rack receiver. Instead, after much research of condensed size, quality, and price, I'm going with folding bikes. Can then place them safely inside the RV.
So, I'd say after 30 years of Dolphining, someone has come up with something for carrying bikes....the inside of a Dolphin!