I have these new style bifacial solar panels that can make power from light from the front or back. 

The panels are mounted on the roof pitched towards the east so they catch the morning light. As they are pitched I can get under them and wonder if its worthwhile painting the roof white or perhaps putting down some aluminium foil or similar to reflect light hitting the roof back towards the underside of the panels in the afternoon.

Anyone tried this?

According to the graphs (as I read them) there is already some light getting through from the back. See below, the blue line is the east facing panels, the ones facing north are in green. My take is that the current from the east facing panels dies down as the sun gets higher, then increases with back lighting in the afternoon....