Depends on the car/pedal placement.. I could do it easily in my E36, but in Audi TT its quite a bit harder as the gas pedal is too far to the right to easily tap with the toe.
Heres a question for you however.. In cars with big turbos, does heel toe shifting cause unpredictable behaviour if you rev it sufficiently high enough into power band to cause turbo lag? I assume if you did not perform the shift perfectly you could cause the turbo to spool up unnecessarily and get a little burst of power you wouldnt be expecting. I just bring this up as I noticed a little variation in power when attempting to heel toe in the Audi, but the turbo is quite small so there is not too much lag. Any ideas from experienced drivers?