SHifting at redline is fine, no problems there. The supercharger doesn't need to spool up as it's driven by a belt so is constantly spinning at a rate relating to engine revs.
You'll probably find that the car is breaking traction slightly when you're hitting into second gear and the ASC or DSC
is kicking in. Ususally this shows a flickering orange light on the dash, but both of my S's have done this without flashing the light before.