Just a thought for you:

I always place all of my packing cubes flat (horizontally) into my luggage. Typically I use one Eagle Creek Pack-it garment folder for shirts and several medium size cubes for other items. The Pack-it folder holds my shirts snugly so that wrinkling is not a problem.

My wife, who is the queen of organization, also use one Eagle Creek Pack-it folder for shirts (women call them "tops"). She lays that flat into her luggage. But she finds it more space-efficient to then place some of her medium size cubes vertically.

If you're a horizontal kind of guy, have you thought about flipping at least some of your cubes 90 degrees to vertical? Would you care all that much if your undies/socks cube gets wrinkled?