I think that both of you guys are right. Mast raising can be easy or it can be hard. It all depends on your age, strength, and whether you have a furler. If you're young enough to bull a mast up and down by hand without a roller furler, and you do a lot of trailer sailing, then by all means build a mast crutch with a roller in it to support the mast. Then attach a single sheave to the rear hole in your bow plate for a 3/8"X60' line to connect to your Jib halyard shackle. All your stays save the fore stay can be left connected to the chainplates and bungeed when en route to the ramp. The sail can be on the boom with the sail cover on, inside the cabin and ready to go on the mast when it's up. At the ramp: Make sure that you set the boat and trailer on a level surface with the wind coming from directly toward the stern. I used to sometimes launch the boat first and raise the mast at the dock but most of the time I did the mast raising while the boat was on the trailer because of the better stability. The first task was to mount my Davis Windex to the extension bracket near the mast head. I used a wing nut for that. Then remove the bungees but leave one on for the fore stay so it doesn't flop around when your raising the mast. I'd close the companionway hatch cover and move the mast aft. This is where the small roller in that mast crutch really comes in handy. If you don't have that, you have to pick the mast up and walk it back to the cockpit. Not such a good idea. Can you stand on the closed companionway hatch on an O'Day 20? I really don't know but this is where I stood when I raised my mast years ago with the 60' line attached to the jib halyard in my hand. This line is of no use until the mast is almost up. Then you can take it around the the mast above the goose neck fitting on the mast so it doesn't slide down. Then pull the slack out of the rope and tie it to the bow cleat. The mast is up and you can take your time connecting the fore stay to the forward most hole in the bow plate. You need to make sure that no stays or turnbuckles get caught or twisted when you're raising the mast.
Now on the other hand,--"four thumbs and a finger",-- if you're a "Geezer" like me and you have a CDI Roller Furler and you only launch once a year and pull it out at the end of the year, by all means go for the Gin Pole. :dance:
Ahoy!
Joe