Harrow said..
The placement for my harness lines is different for each side by a few inches. I've tried sailing at different angles to the wind to see if it caused by heading upwind more on one tack than the other, but nothing really makes a difference. I'm totally clewless about why it is like this.

Saw this in a recent post and it interested me because I'm the same: one tack is 1-2cms forward of the other.

Is my stance is different between port and starboard? It's possible but I feel comfortable. I'm into flatwater blasting on slalom gear so I've also thought that maybe one side's setup to me get upwind, the other to let it go downwind. But Harrow doesn't think that's the case.

Intuitively I feel the lines should be symmetrical (obvious exclusion; serious speed sailing), but I don't know if that's right or not. So are there more to this club than Harrow and me, and/or any opinions on what might be happening?

trousers

ps. Earlier this season my mate Sam's sail became clewless when he hit a carp at speed.

I have one sail like this. I know its the sail because none of my other sails need asymmetric harness lines.
On superficial inspection the batten pockets appear to be tighter on one side than the other. I haven't had a close look at any of the battens yet.

My harness lines are also asymmetric, flat water, waves, across the wind or up and down speed sailing.
All my sails have the battens on the same side, so that may be part of the reason. I also think it's a left hand- right hand thing. my right hand is much heavier callused than the left, so I think my right hand does more work than the left, that's why the lines are further back on starboard and further forward on port.
I've been wondering, if I did weights with my left hand, would this help even my sailing up?

I've definitely had my harness lines positioned asymmetrically from time to time, especially in heavy chop where one direction is against the chop, the other direction more with it. More recently, though, my harness lines tend to be more symmetrical, usually shifted by less than a cm or two. Could be all that winter sailing with mittens forces me to concentrate to really trust the harness. Seems I'm sailing one-handed a lot, shaking blood back down into the fingers of the other hand :-)

This topic is very timely.

Up until a couple of weeks ago (when I bought a new NP Hellcat freeride sail) my harness line positions were pretty much symmetric (NP Atlas sails).

Since sailing with the new sail I have noticed a significant difference in harness line position on differnt tacks (> 1"); I thought I was going nuts!

It is a relief to know that I am not alone; now I can just accept that they are diferent and get on with sailing.

Mind you I would like a definitive reason why they are different but I gues it is a combination of all the factors mentioned above.