Change maximum number of notification icons? My phone shows only three app notification icons in the status bar at most, but there is space for six (most of the time).

How can I increase/change the maximum number of notifications shown at once?

I don’t care if they end up overlapping with system indicators on the right.

I run CyanogenMod 7.1 (rooted, s-off, adb available, compiler as well...) and editing the source is acceptable.
Number of icon to show on status bar depends on programmer how he wrote that status bar application code . We really can't do much here.
You should be contacting customer support of developers of CyanogenMod 7.1
they might consider your request and change it to your needs.