Sure, apart from the special idle condition it would seem pretty odd to have 10º difference in ignition timing between the two cylinders.
Anything over 3º would have me scratching my head.
Fitting the MC21 flywheel (to the MC28) advances the spark by approx 1.0 to 1.5º according to Matt@Tyga in this post.

As I say, I have no experience with the MC28, so that's about as much help as I can give.
Hopefully there will be others that can answer your question properly.
_________________
[color=#808080][size=9]Yes,.. I too know how to waste Time and Money,...