After further reflection (and nudging from comments), I think my arbitrary number of 40 BBs for a daily stop-loss at 10/20 short is way too small. But if that number sucks, what's a good replacement?
If the last month of playing 10/20 short has taught me anything, it's that your bankroll is always quickly moving in one direction or another. Like, seriously quickly. I honestly don't think the 1000 BB bankroll number is conservative at all for that game, especially if you're playing aggressively and multi-tabling.
So that's a $20K bankroll. Okay. You'll see different estimates from different pros, but the numbers I can remember seeing tossed around are that you should never lose more than 5-10% of your bankroll in any one day (which I think comes from the mouth of Lederer), if you're practicing good bankroll management. So that's $1,000-$2,000/day, as far as a stop-loss, which I suppose you should adjust as your bankroll grows/dwindles.
On the conservative 5% end, that's 50 BBs. Hmm.
I imagine there's a very good chance that the above estimates weren't taking the nature of shorthanded games into account, and speaking more broadly. Even so, if you look at the actual numbers, you're running in dangerous waters when your stop-loss is 10% or more of your total bankroll, methinks.
I think the real truth, lurking beneath this, is that if I'm even pondering setting a dtop-loss, I might instead rethink the whole idea of playing 10/20 short. I tend to be stubborn at times, especially when things seem readily apparent and I've worked hard at them, but the simple truth may be that I'm much more suited for full ring play. I'm barely breaking even at the 10/20 short games and definitely not fully situated in my comfort zone.
Those games are very juicy, indeed, but not necessarily juicy for all types of players, especially those who tend more to the tight side, like myself, instead of towards the gleefully-flinging-chips side. I think it's a reasonably telling thing that I've gotten much more upset in regards to poker than I ever have before, in the last month, verging on complete disgust at times. Which isn't much fun, really, in any way.
So, err, yeah. Rambling. I'll probably stick with a 50 BB stop loss for now, even though I know that's likely too small for the variance of shorthanded games. I'm still looking at all this as a working experiment, as far as setting myself up to grind away at whatever limit/game I settle at in a few months, when I slip the surly bonds of Cubelandia.