LA City will not allow double studs to replace 3x studs in new construction,
but will tolerate it in remodels with the stitch nailing as you have
Also, if you are really doing 5 story wood buildings, I would be very
concerned about the axial capacity of the studs which may require 4x's just
for vertical loads. Also, I would imagine your holddowns would be enormous.
You may consider steel frames for the first two or three levels with wood
shear walls on top.
Bruce Resnick, SE
Parker Resnick Str. Eng.