i dont have experience building s&g's, but have quite a few awkward or difficult designs in mind down the line. in order to at least keep trak of things, i'll use the stringline mentioned by mike but threaded down the stitched bow and stern seam by abt 2 in or so from the peak, so it will lie approx on top of at least 3 evenly spaced and exact same length(why not?) winding sticks.

the centrline string will protrude 18in or so from ea end and have a nut or some wt on the end to auto end plumb and possibly taughten. 1 string, 3 jobs.

each winding stick will just have the beam and a clearly marked centrline on it. the stringline will then tell me if probs of twisting or sideways bananaing as it will have to lie on the marked centrlines.

the sticks will be the exact same lenght so that i can also sight down either set of ends and/or use my tape as an offset from either the bow or stern as a sight line if i decide NOT to use a stringline. 3 sticks as thats the minimum to know (by themselves only) if i have sideways banana.

if the process is to use an undefined deck(like in the clc book-overlapped and then trimmed back), it will be important to me to use the multiple sticks as i don't want to just rely on the hope that each shear(clamp) will bend the exact same to say the nearest 1/8in.

this seams(sp) very simple and quick and is the very least i'll do.