By setting:
start: "top 70%" ,
end: "bottom 70%",
ease: "none"
the svg will always draw at 70% viewport height.
Pinning + using once: "true"creates a tonne of space above which I suppose I could change with an onComplete callback function (I think) but I really don't want to use pinning as I'd prefer the scroll speed of the element to change, thus meaning the SVG path draws slower.