Hi Santeri,
Here is an example of such a part:
http://www.ldraw.org/cgi-bin/ptdetail.cg.../61406.dat
http://www.ldraw.org/cgi-bin/ptdetail.cg...582471.dat
http://www.ldraw.org/cgi-bin/ptdetail.cg...521166.dat
Your subparting approach seems good to me...
Here is an example of such a part:
http://www.ldraw.org/cgi-bin/ptdetail.cg.../61406.dat
http://www.ldraw.org/cgi-bin/ptdetail.cg...582471.dat
http://www.ldraw.org/cgi-bin/ptdetail.cg...521166.dat
Your subparting approach seems good to me...