I still say leave it as a 4 day and if you dont want to go on the first, dont! The choice is yours, plus us fellas that like the 4 days still get the choice to run the 4 as well!
As TEAM ORANGE SA has pointed out it can make things to rushed and sucks the fun out of an event.
No matter if its 4-3 or hell 2 days you will never keep everyone happy, but if you take the enjoyment out of racing i would put a good bet on the fact that very few will turn up. As i say 'if it aint broke, dont fix it'