- The hardest part of lowering the mast is getting the rotation right so you don't bind the mast at the front crossbar.
I've never had that problem on the 20 or 17. Rotate the mast to 90deg before dropping and then bring it down.
- I use a ring on the stepping pin at one end and a cotter pin on the other end. (It came out once and was a nightmare.) Two cotter pins might be better if you don't know which way you'll rotate.
You should decide which way you'll rotate the mast before dropping it and then make sure that the split ring is facing towards the front so that it is on top when the mast is down. I don't use anything on the other side (cotter pin, split ring). Just slide the pin in, drop the mast, pull the pin out. I also never sail with the pin in.
- Once the mast is down and on its side, the diamond wire will be supporting the mast at the rear crossbar. Without someone to hold the end of the mast you may stretch, kink, or damage the diamond wire.
Yes, definitely you want someone to go to the back of the boat to hold the top of the mast after you've brought it down. Don't sit the mast on the diamond wire.
I never used any type of side supports when raising/lowering the mast. Probably not a bad idea, but I always just used a second person or a winch if I though it was going to be a difficult drop.