I myself use the two 1/6 inch thick shear webs instead of the single 1/8 inch setup because you have more glue area, and the force is spread out over both sides of the spar. Now the 1/8 inch shear web is probably lighter than the two 1/16 inch setup but the force is spread out more with the two shear webs.
So as a guess, my call is the 2 1/16 setup....
And it will resist twisting more.