Thanks to all for the suggestions!
The following is from my build thread, (Bartman's LR3 build thread - A New Adventure!), but most of it is relevant to this thread, so I’m copying it here (hope that is within the forum rules).
I’m making progress dialing in the new Ender 3. I checked the e-steps for the extruder, X, Y & Z axis. The three axis were all within 0.08 mm over 100 mm of travel, so no adjustments necessary. The extruder only pushed 94mm of filament on a 100mm command, so I adjusted the settings and now it pushes 100.07mm (pretty darn close).
I had already leveled the bed, set the Z Offset, created a bed mesh, and tuned the PID for the nozzle and bed. I then printed a single layer bed adhesion test file, and it came out pretty good, as far as I can tell:
Sorry for the crappy pics - photography is not my strong suit.
The rectangles look like there are no voids or gaps, and they were sticking really well to the bed in each location.
Next was a skew test.
The adhesion of these to the bed was through the roof! I literally had to remove the glass plate and use a scraper as a chisel to remove them.
The XY test was within 0.05 mm (100mm rectangle, 140mm diagonal), so that was pretty good.
The XZ test was also pretty close (0.02mm difference), but there is a lot of stringing, along with a bit of elephant foot. Not sure if that is because of the filament (the white stuff came with the printer, and has been exposed to the air for several weeks), or because I still need to dial in the temperature and retraction settings. Now that I have used up the old filament, I’m going to load up the shiny new red Hatchbox PLA and do those tests next.
The YZ test was a little bit less where I was hoping, with about 0.70mm difference, and again lots of stringing and elephant foot issues. Not sure if this is a reasonable amount, or if I need to compensate in Cura or in Marlin. Once I dial in the temperature and retraction settings a bit better, I plan to re-print that test and see how it looks. I should hopefully also be able to do some of the shorter pieces (pretty much everything but the core, I’m thinking) as is, and maybe try to fine tune it a bit more before tackling that one.