I agree, its safer to drop the mast
If you absolutly must go up the mast, use a climbing harness, making sure you put it on correctly. I have gone up my h23's mast several times. It gives you a whole new understanding of "tender" when your weight goes a bit sideways at the top of your mast. If you have any fear of heights, find someone else to go, or just drop the mast. I would strongly suggest dropping the mast. Working from a harness at the top of the mast is not easy, since you will probably need to stretch up over your head to work. Then there is the issue of dropping things. Obviously put tools on lanyards. But the parts you're adding or taking off are a risk to anyone below, and at risk for being lost in the water. Dropping the mast is fairly simple: we have a small turning block attached to the bow mooring pin, which we run a sheet through from the forestay to the gennie winch. That helps control the mast on the way down, in essence belaying the mast down, and provides both control and power to raise the mast. Other than that, plan ahead for just exactly where is the masthead going to land when you lower it. By the way, there's nothing wrong with asking your neighbors to help. Good luck.Jim Kolstoe, h23 Kara's Boo