LCR,
BTT for a pard.
Never attempted this on any of my guns....but, you're logic seems to be on the right track. Solution likely dependant on how much more plunger-length is needed. I'd be tempted to make a longer plunger from stock material first to see if it's feasible. A longer plunger would benefit from more support (length in rear, inside the frame....and a snug fit). No-harm-no foul if it don't pan out.
I'd probaby look into obtaining a spare hand (or two) before trying to build-up weld on the back of the hand. But, you have a pair of Rugers for back-up
Going on vacation tomorrow..will check-back when I can for progress reports.
Good luck,
Slim