OpenWRT Backfire on WRT54GL signal strenght

Because I wanted my home router to use at least decently supported software that provides complete out-of-the-box support for native IPv6, I recently got around upgrading my WRT54GL's firmware from White Russian to Backfire, which is the most recent OpenWRT release that fits the hardware's limited amount of flash memory.

One issue remains unanswered:

In GNOME shell's top panel and WiFi menu, the signal strength remains at 2 out of 4 bars. Given how the router sits only a few meters behind me, I would have expected much better signal strength than that.

Would anyone happen to know how to improve on these results? Thanks!