I went over to voacap.com and did some modeling to simulate the propagation conditions we can expect for this month. Most people seem to have 20 & 40 meter capabilities as the common denominator, so I stuck with those bands. Here are the coverage maps from my QTH at 0100 Zulu:
20 meters:
40 meters:
VOACAP, especially as implemented at voacap.com, is a blunt instrument, but I think the main point stands out: 20 meter coverage reaches a little bit farther but has a big donut hole, while 40 gives more solid coverage out to a slightly shorter range. Based on this modeling, we ought to stick to 40 meters for these evening roundtables. Based on experience... well, will some more experienced 20 meter operators please chime in?
Some notes on the modeling: I generated the above maps centered on my location, but you can move the coverage around in your mind's eye and not be too far off. The coverage applies for both send and receive (assuming the same power lever, pretty much everybody's running 100 Watts). I used my 'worst' antenna, an inverted dipole with a crummy SWR, so I bumped the power down to 50 Watts and used the 1/4 wavelength vertical option, that was the closest thing available. The receive antenna is a dipole at 10 meters. None of these little tweaks make any great deal of difference. If you try using voacap.com, remember to set the time before each coverage map run (0100 UTC in this case). If you don't do this, the web site resets the time to your closest just-passed hour every time you re-run.