|The RL24 Mk4 is an Australian version that was designed and built towards the end of the Australian production. The drop keel was used to reduce drag and improve efficiency. |
The RL24 is a poular racing boat in Australia where trailer sailers are regularly raced on protected waters, hence the Mk4.
I would be surprised to find anything other than a Mk3 RL24 in America. The American boats are slightly different in rig layout than the Australian boats, generally they are very good yachts with no problems of design rtc.
For general cruising and racing the Mk3 is a much better boat. The keel protruding up into the living space on a Mk4 is not very practical when cruising and the swing keel is safer when running aground in strange waters.