[oillio]

I don't really understand the focus on the 20% thing. I have worked at different sized tech companies, from startup to medium sized, to giant. And I have worked in several capacities, from line engineer, to middle manager, to director. In my experience, it is impossible to measure an engineers performance with an error less than +/- 20%. I have worked on side projects that large and my manager never noticed until I demo'd the results.

Generally, if your manager is not shit and not under unusual time pressure, they should have no problem with a project that doesn't significantly impact the primary work and has some chance of benefiting the company.

Google is interesting as they have an explicit 20% policy, but in practice it doesn't really matter one way or another.