If I have 2 floating xterms open and open a third one, it seems the -geometry settings I give on the command line are ignored and awesome tries to figure out on its own where the third xterm should go. How do I force it to respect the -geometry setting?
In the rules, you have a placement property. It defaults to "place stuff on the current screen where there is the most room".
You need to remove or override this for xterm. You can do this either by adding a new rule or editing the current ones. Adding function() end as the placement function in an xterm specific rule should override the catch-all rule.