Thanks. BoozeKashi! I do think at some point I would like to try a .3 nozzle, but for right now I'm so absorbed in the Blender/design work i can't worry about anything else.

However, I did a good empirical test that has given me an acceptable workaround for my problems with vertical grooves. I took my "icehouse" model that has that same problematic barn door with all the vertical grooves. On my first try with the firehouse those grooves were .15 wide by .15 deep. On my second try with the icehouse I made the boards wider, and the grooves .2 X .2 - they came out like bars. For my test, I made the grooves on the left side of the door .1 wide and .1 deep. On the right side, .1 wide by .15 deep. On the far right, .1 wide by .2 deep.
I also set some of the vertical grooves on the foundation as little as .5 wide, at varying depths, and set the foundation to print outside in, and above the foundation inside out.
What I found is - first of all, outside in versus inside out made zero difference in detail quality.
Beyond that, the deciding factor is not the width of the vertical grooves - it's the depth. The .1 X .1 grooves are acceptable. At .15 depth - quite less so. Amazing the difference 50 microns can make. And 50 micron wide grooves with a .15 or .2 depth look just as wide as the 100 or 200 micron grooves. And - astoundingly - a 50 micron wide by 50 micron deep groove will actually print, although it is just scarcely visible.

So my advice to others is - if you run into this situation where you are trying to print fine surface detail, and you have vertical grooves that are being rounded out unacceptably - keep the vertical grooves as shallow as you can.