To start, 70% is not really enough for most applications. The roof probably got more like 65% due to the difference in height.
Repeating patterns are hard for the system to deal with so you really have to have a lot of overlap for it to turn out.
Avoid sun reflections at all costs.
Look into using the Ground Offset feature in Map Pilot to make sure that the roof gets the desired overlap:
Here are some other support articles that directly address roofs.