Suppose I propose that physical objects have not only "mass" but "massiness", which is "the way things have mass". I agree that we can do the usual calculations using mass and that they will tell us how particles move, but I insist that we do not know that massiness is purely physical; that doing those calculations may miss something about massiness.

I guess that you would have little sympathy for this position. Where (if at all) does the analogy "experience : qualia :: mass : massiness" fail?