In the default skin, there's a white bit at the top right (you may need to view the image on a dark background to see it):
there should not be any margin in the right at all when maximised, so it appears that MB is maximising correctly.
It's 1px in the RH border when MB is maximised. 6px up from the bottom of the caption bar.
I have also experienced the whole caption bar being light blue (the colour 9ido keeps getting in the search box) when the default MB3 skin is first maximised. Can't get it to consistently repeat though.
I will also be looking to adjust and update my old (jistme) skins for v3.
Since you are already experienced in that area, could you please give the details where I should be looking exactly to make adjustments to the skin files and/or images to do that too?
Is the (by now very old) skincreator tool still of any use for that, or should that not be used at all for v3?
Wouldn't say I was experienced, still early in the 'trial and error' stage.
The SkinCreator tool is fine to use, it was the 2.x exe that was overstretching the bitmap header by 2px.
Most skins you won't see a difference in. I found it's been the ones that have elements outside the TrackInfo area and/or items aligned to the bottom of it.
Just check out your skins in MB3 and if you notice any anomalies, check those elements first.