I will give some responses to "bump" your post and see if others reply.
( I have the feeling that posts with at least one reply will attract experts eager to save others from bad advice
I am puzzled that the brass drain flange does not touch the base.
The ones i use have a slight bevel at the outer edge, so that tiny rim does not touch, but the inner 90%(?) does. If you are referring to the outer 10% (?) , that is fine and with the ones i use, that flange only ends up off the drain flange surface of the pan by about 1/32". I agree it would be nice to have a bevel on solid surface pans to prevent ANY standing water outside the flange, but there is very little area there on the ones i use and the caulk squeezed out there hits the vertical step-up and allows no water to collect there (hence the need to make sure i have the drain centered perfectly as I describe further down).
You definately don't want to use putty due to the drain area not being beveled. Being flat, the putty will contine to squeeze out over time (from the 'spring-loaded" pressure of the rubber gasket underneath).
I use clear 100% silicone with anti-mildew agent (typically called "kitchen and bath" and stating "Cured caulk is mildew-resistant"). I snug the lock-ring down a bit (not so much the drain assembly can't be moved side to side a little - just to squeeze out the initial caulk excess). I watch to keep the drain centered, then wipe off the excess. Then i snap in the strainer to keep the drain centered and ensure the strainer WILL fit when the assembly is dry. Then do a final tightening, remove strainer and clean the rest of the excess. I often use a narrow scraper to "tool-off" the squeeze-out and then smooth with a fingertip. I like to make sure that area on the topside is clean (no shiny caulk residue on the satin drain area around the strainer )
Installing the drain on the pan is the first thing to do if you are using silicone. That allows the silicone to set and not allow the drain to move either when setting the pan or when tightening the castle nut on the pipe gasket. Watch the edge of the drain flange when tightening the castle nut. If you see any rotation of the drain flange at all, stop and tighten it later.
After you DO tighten it, a bead of silicone smoothed around the outside of the PVC pipe will cover castle nut and prevent a ring of standing water there for a nice clean drain entry.
Well, hopefully someone will come by and give some more tips (and/or correct me if needed)
 Oh, i don't like the plastic drains either - i have seen a couple of cracked flanges - one of them on a job I did. That was the first and LAST time i used one LOL