Greg,
I was admiring the pictures of your car today. The stance is perfect--not too high, not too low, and the 12mm spacers all the way around are a nice touch on the stock 19s.
I've been looking at pictures of various E90x M cars since I bought my E93 in mid-March, and one of the things that has struck me is that the convertible seems to sit lower than the E90 or E92s I've seen.
I spent a while studying your pictures and my car in the garage tonight, and mine (completely stock) is sitting about like yours is now on the Dinan springs. Of course my wheels/tires are tucked in more minus spacers. I've seen many pictures of stock sedans and coupes that look higher. Could it be that the extra 400 lbs., we're carrying in the E93 are responsible?
BTW, I never thought I do this, but I ordered four 12mm Rogue spacers today. I think you've sold a lot of RE spacers recently. I agree with your conservative approach, I didn't want the 15mm on the front either, and like you, I think that's a good approach until our RACs show up.