This an old post but I did a search to see what others had to say. I have a couple of those dowel centers that I bought years ago and have used on several planes. Didn't realize they were available at hardware stores. Anyway I building a Vagabond with a tapered wing and couldn't get them to give a good mark so I came up with another trick. A pencil is larger than 1/4" so I put one in a drill and wrapped coarse sandpaper around it and ran the drill at high speed until I had the diameter down to 1/4". I was then able to insert the pencil through the holes and mark the fuselage plywood.