The reserve requirement limit is purely theoretical anyway, since the Fed is obliged to pump more reserves into the system to maintain its interest rate targets when commercial banks [net] lend in excess of their current reserves anyway. The UK hasn't had a reserve requirement since 1981.
Agreed (I nearly mentioned it in the original post), and stricter capital requirements now than for much of the period since 1981. (Capital requirements don't entirely restrict the capability of the commercial banking sector to expand the money supply either, but they do require undercapitalised banks to raise more equity funding or similar if they want to continue to expand their loan portfolio)
