Hi GJK
A couple of things to remember about the Remington Noiseless typewriter. 1, The keys do not thrust the type slugs all the way to the platen like your Smith-Corona Stirling. 2, the concept of noiseless is the type slugs just kiss the platen without making the thud or clack of a regular typewriter.
There is also the possibility that the platen has hardened and shrunk very slightly so the momentum imparted to the type bars by the key mechanism isn't quite enough to make a dark impression. My first suggestion would be to try using a piece of 32 pound (120 g/m²) paper as a backing sheet behind your typing paper and see if that helps. All the best,
Sky
We humans go through many computers in our lives, but in their lives, typewriters go through many of us.
In that way, they’re like violins, like ancestral swords. So I use mine with honor and treat them with respect.
I try to leave them in better condition than I met them. I am not their first user, nor will I be their last.
Frederic S. Durbin. (Typewriter mania and the modern writer)