Coming back to this for v2 a couple of weeks later... it's often good to come back with a fresh head to something. Basically I was having a struggle in #FreeCAD... it won't offset on bezier curves, so I used a shape binder instead... but it also has problems offsetting, it kinda works, but also kinda doesn't, and it definitely doesn't for the scale & direction of offset I want.
Today with fresh eyes I reflected on this and... BAKA! (yes, exactly that exclamation is what popped to mind.)
InkScape, which is where the line art was tidied up, can do this with zero problems.
So easy.
I often find using multiple tools is the answer I want.
(I still find it easier to do a lot of 2D work in LibreCAD for example, I have learnt to get along OK with FreeCAD sketcher, but it just isn't my favourite mode for 2D work.)
Kdyby někdo chtěl inspiraci nebo něco podobného pro svoje použití, tady máte všechny díly včetně FreeCAD modelu:
