Is common knowledge that helm changes are not permitted by ISAF rules. But at the highest level of competition crew swapping between events is allowed no problem as confirmed by the Danish Nacra 17 sailing team today.
I tend to agree that helm should not be replaced in the course of a regatta, but in a 4 year Olympic campaign chances are you might miss a championship or two, even if you qualified for them as Santi Lange & Ceci Carranza have done to participate at Weymouth ISAF WC 2015.
Lange has been ill for some weeks and is not being able to race in UK, but Cecilia , who has been training at large and is actually the driving force behind the formation of this team is denied to participate with another helm.
Carranza finished second at 2014 Nacra 17 Worlds with Lange as helm, so it is a reasonable request for ISAF to let her continue training & preparations towards Rio, she even has support of her fellow Nacra 17 competitors like the Danish Team, and the change is taking place for the entire event and not in the middle of the Regatta.
Rules must be followed ,but special cases should be taken in account, more on the investment on time, & effort Olympic sailors put on their campaign plus they are even qualified for Rio already. Image: Lange & Carranza 2nd place Nacra Worlds 2014 by Marine Media Group / Mariano Arias.