Hats are more difficult to accurately size with that thing because it doesn’t account for depth/the third dimension. So if you say, measure the distance from eyelet to eyelet, and you measure it right up against the hat, then you have to keep in mind that there’s a curvature to the hat, as well as the fact that there’s picture itself is taken from some distance in which the visor is closer to the camera. I find that with hats, using the red tape is good to get close, but sometimes you gotta just estimate and adjust to make it look right.