I found and ordered a quantity of SS hex nipples on Amazon that can replace the brass ones used in the prior photo. No luck looking for a 45 degree with mail and female like the brass one. I think I can make one with 2 female threads and use a nipple for the male end. OTOH that 45 degree brass nipple is quite thick, and even if it were to corrode it should be easy to remove/replace.
I am reluctant to modify the SS compression fittings at this time, as they are $20 each. The steam supply setup seems pretty good as it needs only a short curved piece of tube. The blower side is more awkward, but there is plenty of room forward in the smokebox to make a fairly wide curve. I'm not going to finalize it until everything else is set, including the valve piping from the turret.
Speaking of which I'm wanting to use brass pipe for the blower valve connection vs. the copper tube I had before, which I felt was unsightly. The valve (I believe it is from Locoparts) has a female thread on one side and a male solder connection on the other. To use threaded pipe on both sides I needed to duplicate the tube end piece that had been soldered on previously. Fairly easy lathe job starting with some 7/16 brass rod.
Spent the rest of the afternoon setting up the CNC mill to thread the many pieces of 5/16 brass pipe that will be needed. First attempts will be hooking up the blower valve and the whistle.