Join Date: Dec 2011
Location: Morris County, New Joisey
I'm not sure what you mean by "built-ins", but if you don't need 6x6 stock for structural reasons, it seems like it might be overkill. Something assembled from thinner stock as Quickstep described, either purchased or made yourself, would likely be easier to handle & work with, more stable, and less expensive.
The columns on a railing I made for our house many (15?) years ago are assembled from 1x oak, glued up with splined beveled/mitered edges. They're only 4" square, but you get the idea.