Always wear the insulation under. I actually wear the Kuiu Kenai under a guide jacket. The Kenai does nothing for wind so when I stop I put the Guide over the top to cut wind. I also have a Sitka Kelvin which is warmer than the Kenai but doesn’t breathe near as well. The Kenai is my favorite mid layer. It is quiet and breathable. I don’t wear the Sitka because it’s noisy. Has typical sleeping bag puffy coat nylon. Which the super down will also have. Sitka now makes the Kelvin active jacket which is quieter. I don’t own it so can’t comment on that piece. The Guide and Kenai is great for me. Only thing better might be the Yukon rain jacket instead of the guide because it is waterproof, not water resistant like the Guide. It’s a soft shell rain gear but costs so much I haven’t bothered as the Guide does well enough with what I deal with.
When your wearing the Guide over the Kenai, did you upsize on the Guide compared to the Kenai, or did the same sizes work well?
