Maybe you should discuss with them options for achieving what they want without using green screen? Badly done green screen is very distracting and your project is much more likely to look professional and be effective if done simpler.
So if you have an interview for example, simply cutting away to another shot, or maybe compositing an image on top may be acceptable.
It depends on what the project is, but I'm sure there are alternative ways that will end up looking much better.
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http://www.jonbagge.net
Jon Bagge - Editor - London, UK
Avid - FCP - After Effects