The French were fond of making "extra lusso" game guns w/o lower rib therefore it is probably not needed. Isn't there some adhesive out that that can be used w/o heating soldering? If I recall correctly that is how Marlin used to mate top alloy rib to their L.C. Smith guns in late 60s. I would make the gun look good pass it on and move unto something else. USA is full of old second hand guns w/o loose rib issues.