I would like to finish support columns on my porch overhang. The supports are 3 ply 2x6 . I would like to use 1x8 stained cedar as a finished product. The dimensions of the 3ply 2x6 are 5 1/2 inches x 4 1/2 inches. I would like to utilize the full 1x8 cedar, nailed in a "box" formation with the edges lapped alternately. This would leave a space between the 2x6 and 1x8. I was planning on shimming out the exsisting column accordlying with spacers nailed vertically every 16 inches or so rather than re-face the column completely to fit the 1x8 inside dimensions.
What type of nails should i use? Should I liquid nail or glue the edges of the 1x8 cedar before nailing.
I was thinking of cutting the edges on a 45 deg angle as a option. I would like a clean finish that will stand the test of time.

Any input would be appreciated.