Hmm have you played around with the offset to counter that? Also what happens if you open the preset menu and set overscan?
Seems you have the same problem I am having under SUPERPLUS, I have not yet figured out a way to fix that
The the rest works for me now.
SuperPlus doesn't work with the latest cores unfortunately, it's a shame because it really is the best WB mode for AGA (HighGFX is a bit too much for AGA really).
Also about the black borders, the Indivision AGA doesn't do any hardware scaling so it's normally nicer to have black borders for games than to try and stretch a 4:3 display out to 16:9 on a modern display.
This is how it looks on my display (PAL 640x512 WB, the PAL 320x256 for the game).
[youtube]S040ywaoau0[/youtube]