OK, building a road wheelset for a guy 220 pounds, rides "heavy" a pedal masher, rough roads.*
*Actually he's ridden an entry-level set of low-spoke-count Mavic wheels (Aksium??) for 4 years and 5000 miles without issue, so I don't really believe he's all that powerful and tough on wheels)
components we've chosen are:
Ultegra 6800 hubset (32 hole)
H+Son Archetype rims
double-butted spokes (2-1.8-2), brass nipples.

My question-- Would you use 2-1.5-2 spokes on the rear NDS? I like the idea that I can then get the NDS tension up high enough that the wheel for sure won't go out of true, without overtensioning the DS 2-1.8-2; but want to be double-sure the lighter spokes can handle it. Thank you.