I rig my boat by myself, so I tie the "main" halyard to the mast support on the trailer and then raise the mast. when the mast is up and being held on both sides with the shrouds, I pull the main halyard tight and cleat it off at the base of the mast. The mast is not supported at three places and I can climb off the boat to insert the pin in the forstay, this has worked for me for three years. I did have to buy a longer main halyard to make this work.
KH: Yes, I use the jib halyard if alone, and I use a supplementary line attached to the halyard shackle, long enough to secure forward through a turning point on my trailer mast crutch and secured back on a halyard mast cleat, while I go forward to secure forestay. RK
Before I owned a C-14 I raced Lido 14's for some time. I used to tie a 1/4" line (about 25 feet long) tied to a halyard and ran it through the eye on the bow and back to cockpit near the mast hound. Then I walked the mast up to vertical and reach down and grab the line and pull it tight and tie it off on any handy cleat on the mast. Then I walked around and hooked up the jib fore stay. The Lido was especially easy because there was a hinge on the deck where the mast attached. I don't know what the arrangement on the modern C-14, I own an Omega C14 and It may be a little different that the 14.2. But that is another subject I will explore on a new post.