Few years back I have suggested a work around and with big hope that pg would have a setting in biab to use a fixed resolution such as 1024x768, etc.
The workaround is like this: Since biab ONLY get the windows display size at startup, it will position its elements according to this size, we can trick biab not to read the actual size of the display windows. You first change your display size to something smaller than your actual full display size, say 1024x768, and start biab. Then, without closing biab, change back your display to full size, say 1440x1024. Voila! biab size remain at the earlier display size. This is a BIG inconvenience as our desktop icons can be moved around by windows, and this workaround does not allow free sizing.
Beside the "classic" GUI, this screen size limitation problem goes to show the "outdated" programming skills of the folks at pgmusic.