when I do photos I don't planned to stich them together from all corners. Then probably I just take photo every a few meters. In my case from corner to corner is > 20 meters and it was difficult to stich perfectly.
First tried stiching in ptgui using single photos
(without photos of roof) - to many errors. Then I stiched every single 4 panoramas, cropped them (cuted roof) and stiched together in photoshop.
From local gis service used aerial photo of roof and used in nadir.
Check this (not mine) - on church tower (but without zenit and nadir); stiched from single photos every x steps. Available 2 panoramas. On 2nd you can see how the tower looks like.http://zieba.wroclaw.pl/uwg/uwg.html