Back in January, my column for Marketwatch detailed the massive danger that jumbo mortgages posed for U.S. mortgage and housing markets. After months of actions to counter the impact of COVID 19, the potential jumbo mortgage disaster is clearer than ever. Jumbo mortgages are loans that are larger than the limits set for Fannie Mae, Freddie Mac or the FHA to guarantee or insure. During the craziest years of the housing bubble, 2004 through 2007, close to $3.1 trillion in jumbos was originated....