There are better ways to accomplish these goals, like switching to daily rates (or weekly rates). No client worth having cares what your work structure looks like if you're capable of producing -- just move to a day rate, give them your honest best effort, and deliver results.
e.g. Most of my clients are pretty happy with me. None of them would perceive value from me slicing out 7 minutes from an invoice because, e.g., I wrote a post on HN. (They just profoundly don't care about that, they care about the deliverables, the feeling of happiness they get working with me, and -- ideally -- measurable results as a result of the engagement.)