Spring05 - You are right.
As long as an individual is bound by the H1 Visa, one cannot work part time. Actually, you can work any number of hours/week with the employer who holds your H1, but CANNOT work elsewhere.
If I confused you, then here is the explanation:
One would choose to work for part time, only if they have something else lined up for the "rest of the time", with someone other than the employer who holds the H1. And working for multiple employers on H1 is violating the H1 clause.
If you choose to work for fewer hours than full time with your employer and dont work for the rest of the time, that means, you will fall short of the Wages earned for your qualification. Thats a violation to the LC/140/485 requirement.
So its a catch 22 situation, that you would really want to avoid as much as possible.