I installed a 2-1 pipe on a '10 FLHTK with mid frame deflectors. The deflector interfered with the pipe about 1/2" so I took the deflector off and carefully removed material to the contour of the pipe allowing the deflector to fit with about 1/8" of clearance around the pipe. It looks factory and no problems.
The regular H-D accessory deflectors fit fine with true duals, at least they do on my '07 with the Fullsac conversion. No modifications or change to the left pipe routing whatsoever.
I have an '08 Road Glide with the Fullsac conversion. I thought about that before I ordered the deflectors too, but the left side is shaped differently than the right and there was no problem with the fit.