I've taken the poor amount of information they give out and kind of make a guess.
Sitka Kelvin pant is rated as a 170 gram Primaloft fill weight. Problem is they are not specific on which grade of Primaloft they are using. About six different varieties now, I think

I will just assume it is the cheaper original all synthetic stuff. 170 grams is approximately 6 ounces. From what I can find, which isn't much, it takes about twice as much Primaloft by weight to equal the warmth of down. So when Kuiu says there Super-Down pant is 1.6oz I assume that is the fill weight rating

So that leads me to believe the Super-Down pant is just over half as warm as the Kelvin pant. Which just might be perfect for most applications as my Kelvins are way too warm in September and October.
But as I said in my last post,
"I don't know for sure..." I can not seem to get enough information to be absolute. I'm sure there are folks on here a lot more knowledgeable about such things than I. Perhaps they will chime in.