I've got a nice excel sheet with all the info.
Trying to map it to the store.xsd. Quite a job, maybe Access is easier?

If I ever succeed I'd like to help with an extension to SimpleStock import.
What's the current development status of that?

It would seem logical to expand the XML Schema Description with SimpleStock values?
something like
/store/products/product/simplestock,Container, No unbounded
/store/products/product/simplestock/numberstock, Decimal, No 1
/store/products/product/simplestock/trackproduct, Integer, No 1
/store/products/product/attributes/attribute/options/option/simplestock, Container, No unbounded
/store/products/product/attributes/attribute/options/option/simplestock/numberstock, Decimal, No 1
/store/products/product/attributes/attribute/options/option/simplestock/trackproduct, Integer, No 1

Or are there other stock import ideas?