Here would be my concerns: The compatibility between the two solders, and the build-up of solder.
HF 44 is really a soft solder, it will melt long before the higher silver bearing solder will. So basically youre going to attach the rib to old solder using a softer solder. Thats not going to make a very good bond. . Think of using glue/epoxy on a painted surface, no matter how good the epoxy is, the bond is only as strong as the paints bond to the underlying surface.
Also keep in mind that the thicker the solder joint the weaker the shear strength of that joint.
Dont think heating the barrels to 750 caused any issues, just need to either remove all the old solder and replace with new, or fix using the same type of solder that was used earlier.
