DILEMMA

I have a "large" dilemma.............I took down 2 walls of string paper in an office in Reston today (Will finish tomorrow) and started to hang new paper. It soon became obvious that I had overestimated the amount of paper. It is probably going to take about 8 single rolls of paper and I had told them it would be 18. WHAT TO DO WITH THE LEFTOVER PAPER???

This is a major problem because they have used a decorator and the price was probably exorbitant. To return the paper they would have to pay 30% restocking fee, the designer would lose a lot of commission, I would have to admit that I was wrong and I wouldn't get paid as much as I had expected. ( I charge by the amount I hang)

The good thing is that I will be finishing on Saturday when the office is closed. The bad part is, how do I charge them with good conscience for all that paper that I walk off with????????? They have been good customers in the past and are very, very nice people.

How could I have screwed up so badly?????