we're in yuma, i ran a #55 pilot jet, #155 & 2/3 spacer in the summer and a #152.5 & 1/2 spacer in the winter. our air filter is stock, the air box door swiss cheesed and a 19" straight thru dyna muffler on the other end. it ran just a little rich in either case, which i prefer in my air cooled motors, especially for the 6mos that we're over 100* daily. with that jardine on the exhaust, you need to open up the intake air flow in some fashion, K&N cone filter, pull the air horn or swiss cheese the air box door, any one will work. i swiss cheesed because i moved the regulator and extra wiring into the air horn area when i put the sportster seat on, so that space wasn't going to flow well anyway.

I'm in Tucson at 2400ft and like to ride in the mountains(4000ft to 9000ft).  I run a 150 main/50 pilot with #4 (2/3) spacer.  You should be jetted a bit richer than me at 1200ft.

That's why I went to the #50.  I can go full closed on the idle mix and it still runs, best with the #50 is about 1 to 1 1/2 out, 2+ and it starts to stumble.  There are small fuel passages that pull direct from the floatbowl and are not cut off by the idle mix screw, these are apparently enough to allow my bike to idle.  The mix screw just adds more richness to this.  When I went to the #50 I got a good boost to mpg's with no detriment to performance.  Also less low speed deceleration backfire in the mountains.
If your getting any black soot from the exhuast with the #52 go ahead and try a #50.  It's easy enough to change back.
Serowbot