It took 2 hours, 32 minutes, 11 seconds on my 2.5GHz system. But got the
errors below.
The exported STL had lots of holes and degenerate faces.

Compiling design (CSG Tree generation)...
Rendering Polygon Mesh using CGAL...
ERROR: CGAL error in CGAL_Nef_polyhedron3(): CGAL ERROR: assertion
violation! Expr: e->incident_sface() != SFace_const_handle() File:
/opt/mxe/usr/x86_64-w64-mingw32.static/include/CGAL/Nef_S2/SM_const_decorator.h
Line: 326
Geometries in cache: 9676
Geometry cache size in bytes: 38935640
CGAL Polyhedrons in cache: 13
CGAL cache size in bytes: 316064560
Total rendering time: 2 hours, 32 minutes, 11 seconds
Top level object is a 3D object:
Simple:        no
Vertices:  112591
Halfedges:  348212
Edges:      174106
Halffacets: 105486
Facets:      52743
Volumes:        20
WARNING: Object may not be a valid 2-manifold and may need repair!
Rendering finished.

Admin - PM me if you need anything, or if I've done something stupid...

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Thanks everyone! That was such a fast and helpful approach. Ok so it sounds
like this might be a bit of a dead end. My next plan was to try and
construct the entire model in one go but I might try a few alternatives
first.

Thanks again

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