You're over thinking it. The coffee should taste good. If it's unbalanced bitter or sour, it's no good for espresso, if it's unbalanced sweet, it's usually very good for espresso, especially as a base.

The slurp and spit thing is real useful (as in lifesaver) if you have 5 cups each of, say, 50 samples in front of you. For one or two cups, it strikes me as ridiculous.

If you cup a lot of different coffees, need to do multiple samples of each, and have multiple cuppers, there is only one practical method: standard open bowl cupping with ground coffee steeping in each cup, using cupping spoons and slurp and spit. There are simply too many samples to use filters or presses or to swallow, and too many people to have lips touching the cups. The most widely used standard here is a coffee to water ratio of 55 grams per liter, 200F +/- 5F water, press pot grind, 4 minute steep time, break the crust, 6 minute cool off time, and taste.

If you tasting a few or one cup, with one or a few people, use any method you please. Personally, I like to steep the coffee four minutes as in cupping or presspot, then pour it through a paper filter into a wine glass, so I can smell it more easily. I use roughly 60 grams per liter; the SCAA brewing standard is 55 grams, the SCAE standard is around 70 grams. Since a normal after dinner demi-tasse is double strength, so you can brew over a really wide range of brew strengths without any problems. Pick whateve strength you enjoy most.

For tasting coffee analytically, avoid drinking it too hot, since it blows out the palate. Use the baby bottle trick: touch the cup with the inside of your wrist. If you can hold it there comfortably, it's cool enough to drink.

NICE! Great post as usual!

Got it, thanks, will report back on the Bolivia shortly.

Report on the Bolivia:

Ground 14g and added 8oz of 200ish water to it in a Bodum double wall cup:

@04:00, balanced overall, nothing bad, no sours no bitters. Some very light notes of caramel with the slightest possible hint of acidity. No aftertaste bad or good.
@10:00, maybe a tiny bit more caramel, all else the same.
@16:00, ditto.
@28:00, slightly bitter with everything else gone; not, at all, as bitter as the Brazil above. Some slight, slight, bitter aftertaste.
@45:00, maybe more balanced than 28:00, with some sourish/bitterish short aftertaste.

What does that say? Any benefits of repeating this after a 6-day rest?

Checking on my Caveman Syndrome, I added a bit of sugar @60:00 and now it's like I'm drinking a diet-wine (if one was ever made), literally .

Bolivia shot after a 4-day rest: acid! Might need to wait till day 8 before trying again.

Bolivia shot after a 6-day rest: much better than @ 4 days rest, more like espresso than acid, but too acidy. Yup, will wait till day 8 before trying again, I have a feeling this one won't be OK before day 11.

Bolivia shot on day 9: just like on day 6, too acidy; even in a 5oz cup with steamed milk.

I'm having a hard time following what you are doing. Are you trying to make espresso with light roasts, or cup dark ones? Neither of these usually work for me.

If you brew a roast that you pull just as the first crack is done, and taste it cool, and it tastes mostly sweet, like a grown up soft drink (think a good lemonade) or like a late harvest wine, it will work for espresso. If it tastes predominately tart or bitter, like a dry wine, it probably won't work. However, you still need to roast medium for your shots, and this brewing test does not work with medium roasted coffee.

Let me recap: roasted the above Bolivia on 5/22, cupped on 5/23, pulled shots on 5/26, 5/28 & 5/31 but with no good results; still hoping it will mature in a few more days.

I understood this brewing test (cupping is what I did) will work with this level of roast:

On my setup it goes like this (with BT):
<400---------------- <420---------------425----------------430------------ ~435
C1starting------------C1ending-------------------------------Bolivia---------C2starting

What are the ranges for light, medium and dark above? I understand that: light < 425 < medium < 435 < dark.

I'm sorry if I was not clear the first and second time. There are two different roasts: cupping roasts pulled, just after the first crack ends, and espresso roasts, which mostly go at least to about 5 degrees before the second crack starts, and which usually use a slower profile as well.

I'm not going to advise you how this works out on your roaster, since that never works; but you do need to do two different roasts.

Also, the espresso police will not come and drag you away if you occasionally brew coffee to use up your cupping roasts, and you'll become a far better roaster if your try all your coffees roasted light as a matter of course.