My cruise ends in Shanghai, questions about visa

We have a terrific hotel booked and we've already bought our business class air tickets for a 4 night stay.
First, I read some place that arrival by ship does not qualify for the 3-day visa anyhow. But, second, short of rebooking our flights a day earlier, is there any way to request an additional day? I am assuming they will not let us land in Shanghai without a proper type one if our flights are more than 72 hours away. We are visiting Hong Kong prior to the cruise, visiting Taiwan and Japan, but making absolutely no other entries to China or going beyond Shanghai. In 1996 we went on an extensive tour of China, but due to illness we didn't get to see Shanghai. I've read that having a past one is a plus.