Ignition timing question...?

This should initiate some good debate...

I've always understood that ignition timing should be set with any
advance systems (vacuum diaphragm, etc.) disconnected. I tried to set
up my '87 Accord that way, and I can't get anywhere near the 20-degree
timing mark with the vacuum advance disonnected. Leaving the vacuum
line attached, it jumps right close to the 2-degree mark and seems to
run well, if missing a little "jump". Oddly enough, when I accidentally
took a test drive while forgetting to reconnect the vacuum line, it seem
to have a lot better pick-up when I punched the gas...

Anyway, I'm looking in the shop manual... the directions say to
disconnect, test, and then plug the vacuum lines, then goes on to list
the proper timing settings for various engine/transmission setups, never
specifying that one should reconnect the vacuum lines, and describes how
to adjust the timing by twisting the distributor. So far so good...

BUT... all the diagrams show the vacuum lines still attached... AND the
next step tells how to check the cold-advance operation (on engines that
have it), while the following step THEN tells you to disconnect the
vacuum hose(s), plug them, and then check the timing with an advance
meter, listing way lower advance settings than the previous chart.

Example: the first chart
(http://moltenimage.com/freebies/g3accord/engine_electrical/24-4.JPG)
shows that the A20A2s should be anywhere from 10+/-2 to 20+/-2 degrees
(depending on variant and transmission) - it doesn't specifically say
the advance lines should or shouldn't be connected, but you see in an
earlier step that they have been disconnected and not reconnected.
Meanwhile, the subsequent step
(http://moltenimage.com/freebies/g3accord/engine_electrical/24-5.JPG)
says after disconnecting and plugging the hoses, all A20A2s should be 4
degrees.

So what's the story? Experience indicates that timing should be checked
and set to 20 degrees (there's an actual "20-degree" mark on the
flywheel) WITH the main advance line connected. Old-school knowledge,
however, suggests that the line should be disconnected and plugged, but
when I do that, it's impossible to get anywhere near 20 degrees (and
really, old-school knowledge suggests that 20 degrees BTDC is an
*insane* amount of advance for ANY engine).

I've seen this topic generate a lot of debate on a couple boards over
which is the proper procedure... just wondering what the concensus is in
these parts?