Actually I've had much success with FNM/FRE. When I started pairs trading them the spread as I recall was about 14 points. Now it's in the 5 to 7 range. Somehow I managed to turn profits. Looking back at my trading for 2002, I pairs traded FNM/FRE 84 times without a single loss! OK, sometimes I cheated and sold my long position while continuing to hold my short position or vice versa so I wasn't true to pairs trading.
