Only 20% in gold? In Harry Browne's book "Failsafe Investing" he puts 25% into gold.
With his recommended fixed asset allocation ("Permanent Portfolio"), $100 grew to $1800 from 1970 to 2003, with losses in only four years. This is 9.2% per year, and 4% per year over inflation.
To learn more, you will have to buy the book!
Of course, we gold bugs have even more than 25% allocated to precious metals or commodities.