Staying 8 days in Shenzhen and Hong Kong

You can fly into Shenzhen, stay for less than 144 hours, and then head for Hong Kong to avail yourself of the 144-hour visa-free transit scheme in Guangdong.

Joe, thanks so much. I want to fly into Shenzhen on a Thursday, spend a few days, then go to Hong Kong, then back to Shenzhen and leave from Shenzhen the following Thursday. So this would be more than five days, more than 144 hours in total. Is this possible without an official Chinese visa? If so, what should I ask for at the airport in Shenzhen upon arrival? My biggest worry is then crossing back from Hong Kong to Shenzhen and then getting on the airplane. What would I need to ask for at the train station in Hong Kong before boarding the train back to Shenzhen?
Joe, thanks so much and really appreciated.

Shenzhen transit without visa is still very new and there are not many reports yet. When you check-in for your flight to Shenzhen, the rules say that you must have a confirmed onward air, bus, cruise or train ticket to a third country within 144 hours, starting from 00:01 on the day following the day of entry. If you don't have an onward ticket in your hand when you check-in for your flight to China then you might be denied boarding. Also when you return to China, you must either fly or else see if you are eligible for Shenzhen VOA.