I've finished my 1:100 scale Blender model of the Covenanter.
Now I'm trying to get it uploaded to Shapeways for 3d printing, but for the moment there appear to be issues — the trouble is, I have no idea if the issues are with the model, or with Shapeways' servers, which have been known to crap out fairly frequently, especially when somebody has been trying to make "improvements" to them.
EDIT: It's now available for sale at https://www.shapeways.com/product/PJ4PVBAJW/covenanter-15mm
Something was bugging me about the proportions of the tank, and I finally put my finger on what it was — the road wheels were riding too high, so it didn't give the exaggerated gap between the running gear and the track-guards that was seen on the actual machine. So, I adjusted that and now it looks a bit better.
It could be taken a little further still, but then I'd be running into strength issues in the printed model. So, this will do the trick I think.