Hi all, thanks for the great replies. I just typed up this post and it turned out quite long. I seems that as I get older I more often go into "story-telling" mode. Please bear with me.

After every post I realize I forgot another variable or two that are important to mention. Aside from the obvious things like the placement of tip in pitcher, I think these are relevant to mention:
- @4 oz of whole milk in 12 oz pitcher
- burn-me steam wand
- steam tip: 2 small holes
- steam tip: 2 large holes
- steam boiler temperature: 255 (max)
Initially I had the steam boiler temperature set at 250 but for the last four or five attempts I've kept the temperature at 255, which I think is the maximum the PID will let you set it to. This way I can purge the wand all I want and still have a lot of steam/pressure. It seems that the boiler gets back up to temp really quickly too, which helps. Also, this should elminate the possibility of not enough pressure being the problem. Incidentally, I haven't noticed a lack of steam power on the Duetto, not when steaming 4-5 oz of milk anyway. There's more than enough to get the job done.
At some point I realized that when using the 2-hole tips the orientation of the holes in the milk relative to the pitcher may be important. (Ok, maybe that's a "Well DUH" statement!

) For me, when I have the holes in a (roughly) vertical orientation and the tip on the side of the pitcher I can get an excellent whirlpool everytime. You can get this orientation easily by just swinging the steam arm just off to the side of the machine.
Chris's advice was to skip the stretch part of steaming and keep the tip a half to three quarters of an inch into the milk from the start to the end.
Using these two ideas I practiced using the soap-water trick until I consistently got a whirlpool; I was able to do it three times in a row so then I tried it with milk.
Using the tip with the small holes I followed Chris's advice and had a great whirlpool going the whole time and stopped it when the pitcher felt too hot. I ended up with steamed milk, but no foam whatsoever: it was the least foam I'd ever gotten. I was still smiling though: it was the best whirlpool I'd ever done!
However, just because we
think we're doing something doesn't necessarily mean we really are, so I wasn't going to give up on Chris's advice yet. Besides, one should extend the benefit of the doubt to those with a lot more experience. So the next time I tried the same thing, orienting the holes and tip the same way, but with the larger holed tip. Awesome whirlpool the entire time but the milk got hot very quickly. I did a little foam though.
I decided to go back to the tip with the small holes for this quantity of milk.
The next session I tried to raise the tip a little and did end up doing some stretching. I got some bubbles but nowhere near as big as I had in the past. However, I stopped the stretching early and the whirlpool gobbled them up right away. Foam was pretty good, but probably too thick for latte art.
Last night I tried again; I don't remember if there was any accidental stretching but if there was it was minimal, then textured the rest of the time. I stopped earlier than I have in the past and there was a decent amount of foam, and when I swirled the milk there was a definite "wet paint" look.
This morning was the best yet. I kept the tip just slightly below the surface and textured the entire time. No problem whatsoever with foam, in fact I wonder if it was in between latte and cappa consistency. I easily could have gone a bit longer and had even more foam.
So far the best results have been with the tip close to the right edge of the pitcher with the tip just below the surface, texturing the whole time. I'll keep experimenting with the orientation of the pitcher and when to stop. In these last two attempts I didn't have the pitcher tilted right as much as I had previously.
Older posts talk about replacing the steam arm in order to use a particular 4-hole tip but Chris has the
Pasquini 4-hole tip available which looks like it will fit and it's only $14, if anyone's interested.
Thanks to everyone for your comments/suggestions!
d