I have used solder paste for a variety of "fixes", I used it on my fowler underlugs and tried to knock one off with a hammer just to see how strong the bond was, I couldn't knock the lug off.
Fast forward; somehow, I screwed up the rear lug on the steel trigger guard (second build) and found out I needed a longer one. I cut off the old lug and used solder paste to install another one. 10 years down the road and a bunch of wood miles, it is holding just fine.
I have used the paste for underlugs, other lugs, adding metal to a trigger bar and other things, I have never had a failure so far.