Hi chris,
i had this problem for the last two years untill this september when i went for the santi drysuit and undersuit (bz200), i havent felt a touch of cold since
and have never been warmer,my buddy also has the same suit and undersuit and has do 2.5 hour runtimes to 73m in the baltic with a water temp of
4oc and he cant talk highly enough about it,the 400g like jim says is seriously warm,only thing is that i think you will have trouble fitting this under the
othree suit,if you want to try mine your more than welcome,only thing is mine is made to measure and im 5/10,but im sure my buddy would give you
a go of his,he is around 6/5ish,they are a serious undersuit made for baltic waters,just my 2cents worth!
chat soon: Mark