I can't heel and toe in my 2013 Plus 8 (which i believe is the same chassis as the S4 or S5 Aero?).
Pedal box is super tight with my big feet, and the pedals heights aren't helpful either.
I tend to blip on downchange anyway so that's just habit, but either before or after braking depending on the exact situation on the road.
So no, you're definitely not alone.
I think most of the later Aero chassis'd cars are autos though so we're probably in a minority already :-)
