Solved

Changing from 50% to 75%.

Hi guys, 
our league has agreed to change the race duration from 50 to 75% on the day of the first calendar race (today) Some of us have already done the tests and there's is no change in the rate of tyre usage or in number of total laps (under strategy). My question to all is, is the change as the one we have made effective on the same same day, or is it only effective the following race after the change has been implemented?
Another question: is it possible to change ( let's say) from 75% race duration back to 50% in the middle of the season?

Thank you 
BC 

The change in race duration takes 1 race day time to come into effect so for your next race the duration and tyre wear etc will be changed. 

@MS thought that got stopped after the vote around 6 weeks ago after the compaints of hosts abusing it but know the vote went to only allow 1 distance for season same as changing number of days raced

Maybe after 1 race is run new duration will be applied and then cannot be changed for full season. I haven't personally experienced this so not 100% sure. 

Thanks for the replies guys. 
The changes came into effect the flowing race day, right after race 1 had finished. 

Thanks for the support 

Ben Cabral