Interested on peoples take on layering a Rab Borealis. It is my first soft-shell (/wind shirt) and it is exactly that - a soft-shell, but looks more like an outer layer. Obviously I can wear it at this time of year, over a base layer, but when it starts getting a bit colder or up on the summit, would you go:
Base, R1 - Borealis over the top when needed
Base, Borealis - R1 over the top when needed
Base, Borealis - R1 as mid layer when needed
It's going to take a while getting used to it being not tight, but fitted and short (as in belt line) - I do have room in it even over the R1 and can stretch fine - i'm 6', 34 waist, 13.5 stone and got a large - i'll have to test it out on the hills next weekend but just wondering if anyone else has suggestions?
The advantage of layering is that you can mix and match as you noted. Essentially, adapt the layering to suit conditions & activity; suck it and see is probably the best advice...
The windshirt will stop warm air being stripped from the layers underneath it. So your first option will be warmest, as all the insulation (base & mid) will be protected under the windshirt. The third option will depend how much you want to faff with de-layering.
I agree with both - R1 over base and Borealis over the top when needed. Both are large and I feel the R1 is maybe not tight enough and the Borealis is a little too tight but field testing will prove this. (and I did think that the R1 on top of the soft-shell seemed a bit crazy but that doesn't mean that people don't)