Thanks for the suggestion! I played with query, and while that alone didn't fix my trouble, it was interesting to see that query and as_q both seem equally good replacements for the default q. In all my research on the problem, I hadn't come across query as an option.

Your reply prompted me to tackle the problem anew, and in wee hours of the morning, I did solve it. The solution is a little anti-climactic, but I'll note it for posterity and prosperity. Watch for a new post soon.

Thanks again!