Hi Adrian,
When you use a solid hatch, are you deleting the triangle curve that you use to set its boundaries?
If you’ve tried deleting the curve and that doesn’t work, it may be because Shaper expects the triangle to be defined using the svg polygon construct whereas Rhino creates it using the path construct.
Are you aware that Brian Gillespie created a Rhino plugin for Shaper Origin svg export? I don’t know whether he’s got as far as including custom anchors but worth a look. It is available in the Package Manager and is called TunaHalf. There is also a discourse thread which may have helpful tips at Shaper Origin SVG Export
Regards
Jeremy