6. Temporarily abandoned 5., getting closer but there's always another
problem to be evaded. Instead, will try using rawtogrim.f90 to convert
straight to GRIM. This will include non-land cells but for comparison
purposes that shouldn't be a big problem...  noo, that's not gonna
work either, it asks for a 'template grim filepath', no idea what it wants
(as usual) and a serach for files with 'grim' or 'template' in them does
not bear useful fruit. As per usual. Giving up on this approach altogether.