I've done the gin pole method using boom as a gin pole on my C&C24 and did not like the swaying as the mast is at the low position (boat in the water). While researching the stabilizing system i found Catalina 27 A-frame and built one for myself. The only difference in my case from the original design was that legs of an a-frame were secured to the toerails instead of chainplates. I am way more pleased with this system as the control of the mast is superb.
There is a very good video showing the system in use on Youtube
Dropping the Mast - YouTube
Hope this helps.