I really want to do this just so I can get some time to work on my own projects. How did you sell this to your employers (or are they one of a very few shops which do the 4 day week thing like Treehouse)
"I want to work 4 days per week".
"OK, no problem, we will reduce your salary / bonus etc by 20%".
Time passes.
"Ok, I am doing the same job for 80% of the salary and I never make my bonus".
":)".
I know that being a salaried employee is different, but if you're letting people work you into 10-hour days, don't.