Having trained in some old 172s, I appreciate regulations that require updated weights and balances with a licensed mechanic when the owner does something like

Having trained in some old 172s, I appreciate regulations that require updated weights and balances with a licensed mechanic when the owner does something like upgrading avionics. So I understand the cost of keeping those things airworthy. But in my case, that same plane has a seat rail lock that fails during takeoff. Luckily I had an instructor with me who grabbed the yoke when I had to let go. It's a weird world where you're confident to not rent a plane that will stall because of some aftermarket install, but you're on your own if that old seat fails.