Currently using 4th Element Xerotherm base layer (top and bottoms) when it gets at it's coldest I add a merino top and leggings. A few things made a big difference, dry gloves but not wearing liners that were too thick. As counter intuitive as it might sound thinner liners were warmer. Same issue with socks, thinner was warmer. I'm guessing that too thick gloves and socks somewhat restricted both blood and air flow. When it's at it's coldest I add an additional KG of lead and add more air to my suit, this helps. I try to dump and add air as little as possible.