If you're gonna wear it open primarily you could probably get a VI. Otherwise VII is your best bet.
The weave is very very open, so it's sort of stretchy, but fragile-feeling, if that makes sense.
Joseph from Suspension Point says:
The Cardigan Drips is meant to be a slim fit (and it fits a little slimmer than some other size V pieces from Schneider) but I still recommend the size V because it is a lightweight, open weave knit and as such there is some stretch to it (you can see the detail of the knit in the final photos on the product page) so it adapts well to your body. I own this cardigan myself and it is really comfortable to wear and works well as a light layering piece because of how breathable it is.