I know this is Porch & Decks, but I didn't see a forum for fences and I hope this is close enough to be appropriate :-O

I'm building a fence with boards placed horizontally; not prebuilt panels, just lumber. I have 4x4s being set by a professional right now, and I'll be buying 1x6x8 ground contact pressure treated boards.

My plan is to nail a pressure treated 2x2 to the side of each 4x4, then I can nail the 1x6 to the front of the 2x2 to make it flush with the 4x4.

Here's the 1x6 that I plan to buy:

https://www.homedepot.com/p/WeatherShield-1-in-x-6-in-x-8-ft-Ground-Contact-Pressure-Treated-Board-253935/206974075

and the 2x2:

https://www.homedepot.com/p/WeatherShield-2-in-x-2-in-x-8-ft-1-Pressure-Treated-Southern-Pine-Lumber-302477/100023713

(I can't find a 5' 2x2, so I'll have to manually cut each one of them :-/ )

Something like this mock-up; you can see a vertical yellow stripe next to the dark brown 4x4s and behind the medium brown 1x6s, then a third one down the middle. That yellow represents the 2x2s:

I'm looking at this nailer, which is something I'll probably never use again so it's really just for this job:

https://www.homedepot.com/p/NuMax-Pneumatic-21-Degree-3-1-2-in-Framing-Nailer-SFR2190/202101759

I need for the 2x2s to be solid, of course, so I figured a 3" nail? The pressure treated 2x2 will really be 1 1/4", so that's 1 3/4" of nail in the 4x4. Assuming that my air compressor can hit it hard enough, I guess.

https://www.homedepot.com/p/Grip-Rite-3-in-x-0-131-in-Plastic-4M-Vinyl-Coated-Steel-Smooth-Shank-Framing-Nail-4-000-Per-Box-GR014/100394346

Then, the 1x6 is really 3/4", so I figured two 2" nails on each side (6 for each board, connecting the 1x6 to the 2x2s):

https://www.homedepot.com/p/Grip-Rite-2-in-x-0-113-Gauge-Galvanized-Steel-Ring-Plastic-Round-Framing-Nails-1-000-per-Box-GR04HG1M/202275372

I wish that I could find nails that didn't have shiny heads so that they would blend in better, but I don't see anything like that :-(

Thoughts, ideas, or suggestions? As I said, the 4x4s are being installed right now, and I'll be ordering everything this week.

Thanks in advance!