I am having this issue where the side bar doesn’t keep the size I set it to. I am not sure how I reproduce it, but it has happened a couple of times. I could reproduce it once by while in dual mode I add a new finder tab (not TF tab), the sidebar grows in both sides to the largest text size. Doesn’t always happens, though.
Maybe add a lock sidebar size?
This one hasn’t happened again, so, let’s hope it was a one time thing.
I have the same problem (also on Mavericks) and it is very, very annoying. Every time I open a second tab with ⌘U, the sidebar on both sides of the tabs grows its biggest width.
I would be very pleased indeed if this bug could be solved.
Please update to 1.5.5, it should have this issue resolved: