En outre, dans ces discussions, tu trouveras des retours utilisateurs de 7D qui vont te confirmer que ça marche :

600EX RT + transmitter + 5d MK2 Sync speed
I have st-e3-rt + 2x600ex-rt on a 7D - hss works and initially i didn't think there were any limitations.

http://photography-on-the.net/forum/....php?t=1300126
I have been using the 7D with the ST-E3 and 600 EX-RT's for over a year now.
Never had a problem with sync speed of 1/250 on any of my images. Never had a problem using HSS too.

Et plein d'autres encore...