You should be able to eliminate chain rub with a double without too much difficulty. The triple FD should work just fine with double, and the feather adjustment in the shifter should allow you to adjust derailleur position to eliminate rub without shifting chain rings. Its a matter of getting the cable tension dialed in and limit screws set.
When you say the feather adjustment, are you talking about the "half clicks" that seem present? I noticed that, and was thinking that's what they were for, makes it almost like a 2.5 speed in the front (this click for your big rings, this click for your little ones on the RD).