@MikeMachado, it looks like the 1000mm uses the 20mm size (X-Carve 1000mm Drag Chain), which would be SKU 30331-05. I’ll know for sure if someone else confirms it, or when I receive the totality of my order in “3-4 weeks”.
As for the quantity of extra drag chain to go from 1000mm to 1800mm, I ordered 3m*. That number is an educated guesstimate.