"Force 44" is nothing but repackaged Harris-Welco "Staybrite", a 95-5 Tin / Silver,.........the spec'd liquid flux provided is sudden death for bluing,.....adjust your sails accordingly.
I worked 10 years just a few feet away from the production line that made that stuff. It's the bomb.
If you ever make a pilgrimage to the Point Blank Shooting range in Blue Ash Ohio, the main entry is right where they made Staybrite for years when they were at that location. I helped move them to the new facility in Mason.