Mike.
In reply to your question.
I think it would be a bit "messy", and not give any real advantage over the maker's spring. Still giving variable lift, depending on head position......
I can understand you, not wishing to modify your brand new machine, until you've gained some confidence.
How about, installing the machine in it's working position.
Then lasso the head, and run a line/ cable upwards over a wall or ceiling mounted pulley, with a balance weight on the end.
My workshop door closer, has worked on this principle for some 10 years now.........
David D