If they had done it correctly in the past and the results you provided were good, then why did they make this huge change? I would tell them that it is going to take 3-4 times longer because they chose to do it over white. Then negotiate with them from there. If this is a repeating job, you have to play your cards right to ensure future work, but you definitely want to impress upon them that this was a huge mistake. Often the only way to do that is by asking for more money.
I bet you wish you could reach through the screen and rip that white sheet off the wall. Unfortunately there still is no plugin for that.
Good luck. Find some good roto music. Jimi Hendrix always works well for me.
Reiner
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