Yes, the CSL would work on the M, but the M wheels with the tyres would not work on the si. That means either buying another set of wheels or change the M wheel tyres. Not sure I would want to store the M wheels as there would be no plans to sell the M if it is as good as it seems to be.
I have not 100% decided on that yet, so once I have the M here I will have a look how it is all going to work. Also, not sure about the CarPlay system as it would depend on a buyer for the si if they are prepared to pay the full price I paid for it just over a month or so ago, otherwise I will remove it and put it in the M. Same for the GapTech that has literally been used twice :lol:
I will have both cars garaged for a bit whist deciding :lol: