Replacing upper shrouds in the water

[Hermit Scott]

When I replaced the forestay/headstay (whatever the technical term for it is) on my boat, I used a halyard to the chainplate then went up the mast to disconnect the top of the rigging.
I want to do the same for the upper shrouds but the spreader is an important part of keeping the mast up.
Can I do the same thing with a halyard and run it from the mast head straight down to the toerail with out having it on a spreader? Is that a safe way to keep the mast from falling sideways while I am 40' in the air?
The boat has 4 lower shrouds as well.

 

[RAD]

Yes.....as long as you have the halyard as the back up there should be no problem

 

[Ted]

When you hoist yourself up the mast try to keep your weight on the same side of the mast as the shroud you are replacing. The more loaded shroud will be the one still on the spreader.

 

[Hermit Scott]

When you hoist yourself up the mast try to keep your weight on the same side of the mast as the shroud you are replacing. The more loaded shroud will be the one still on the spreader.

I guess I will do it on a very very calm day. One time I went up a mast I was all over the place like a rodeo. I thought about the "being on the same side as the disconnected shroud" but if the boat leans to the the side of the connected one, it doesn't do much good.
I forgot to check what type of connectors and thread type the shrouds have. Now I have to make another trip before I can order them.

 

[Sailm8]

I make a seat belt for around the mast when I get to the top. Not my first rodeo.