How would one go about sizing these on a rockered ski? I have the new Gotama's (137-106-122) with the rocker tip and tail. I'm thinking that getting the 140 to give me full coverage on the tip is a waste since #1 it's rockered and by definition won't have much pressure and #2 most of the traction comes from the back on any ski. So I was thinking of going 125, but then I'm thinking with the rockered tail maybe it makes sense to go with the 110 and just worry about full coverage under the foot. Thoughts?

You size skins for rockered skis the same way you do for regularly cambered skis. You look at the tip and tail dimensions and figure out what size will get you the most coverage. Some people will say you want to get the size that will completely cover the ski base from the tip to the tail to maximize traction. The fact of the matter though is that when you are skinning, especailly with a ski with tip rocker, most traction is generated in the back 2/3 of the ski. So from a little bit in front of the binding on back. Also, we're talking about millimeters here. A very small measurement. So if you went with a 125mm skin, which I think you should, based on the gotama's dimensions, you will get complete tail coverage, and complete coverage underfoot, the two most important areas for traction. And in the tip at 137, there is a difference of 12mm. That means that you have 6mm of base/edge on each side of the skin. That is just over a 1/2 a centimeter, a very small amount, and the amount that will probably have to be trimmed away anyway to expose the edge. Bottom line is the 125 is your best bet. No sense in paying more money for material you will just end up cutting away anyway.

The traction you get from skins is mostly in the back of the ski, but getting full coverage would be good if you're going to be hiking steeper terrain. You could do fine with a 125mm, but 140 would give you total coverage. If I was going to buy new skins, I'd get the most coverage possible.

I would go with the 125 for sure. The price difference is minimal and the more coverage the better.