I’ve had a Martin jig for about 40 years. It is poly-carbonate material. I’ve always used the straight clamp that does a fine job with off-setting. Just this week I got a right helical clamp for it. I’ve only tried one sample vane for set-up purposes and I’m very impressed with the results. It’ll be seeing a lot of action shortly. It is a basic jig but very effective in what it does, which is is one vane at a time.