I cut and installed the starter newel today. It took me almost all day to cut and fit it, as it was one solid post (actually it is filled with poplar 1x or something similar), and was too deep for my circular saw, and with the molding, too akward for my table saw.
In the end, I started the cuts with the circular saw and then finished it with chisels and a flush trim router bit. It took forever to hog out that space, but the final fit was worth it. I was able to cut it to height by using my power miter saw and going at it from all four sides. It just fit beneath the blade on the miter saw.
Once I had that done, I had to chip away some of the tile flooring (the whole tile floor will go away and be replaced in the future, but not for a while yet)
Then I clamped the newel to the stairs and plumbed it up. Once I had it plumb, I tightened the clamps, rechecked plumb, and then drilled the installation holes. I drilled the forstner bit holes first and then used a long drill bit for the screw holes.
I used 3/8" hex-head lag screws to install the post. Two on the front and two on the side made for a solid assembly. I did not use construction adhesive, although that would have been a good idea. I may disassemble for sanding and some preliminary finishing, and then glue it in place for the final assembly.
Also, I found a seller on ebay who was willing to sell me enough 41" balusters at $1.75 each to do the balcony rail. I couldn't pass that up, as the cost was less than half of the cost new. I purchased those and will be using them on the balcony (main floor) railing once they come in. That allowed me to change the rake rail height to 35" on the stairs, and the balcony rail (guard) height to 43 3/8".