In XFCE 4.2b1, the panel's with (Small, Medium, Large, Huge) is a scale size off from the iconbox. In 4.05, whatever size I chose for the panel was correctly mirrored in the iconbox. I can provide pictures if necessary.
Created attachment 70 Discrepancy in "Small" size
Created attachment 71 Discrepancy in "Medium" Size
Strange, I don't see this. It may be theme related. What happens when you choose different themes?
I just wanted to note that I realized (after installing them on my laptop) that this problem is from the 4.1.90 Debian packages. This might be potentially resolved unless those are as new as it gets. (I apologize if so.) Anyway, I tried many combinations of UI themes (Window Manger themes seem to be irrelevant), and the problem persists. Perhaps you have a plugin on your panel that is making the panel larger than its smallest size?
I can't really find it in the code, I'm afraid. If someone else would like to take a look at it, that would be great. Reducing severity and priority.
This works fine for me, the code is correct, as far as I can see; please reopen if it still happens with the next pre-release (RC1).
Move bug to Window Buttons; the merge of tasklist and iconbox.