I may be wrong, but I don't think Google Earth has ever made any great claims as to the accuracy of their images. They have certainly never said the stuff meets survey or engineering accuracy standards. Just using street address in Google Earth the closest fit I can get on cross hairs vs image is around 200 feet. For real accuracy their control network for their images would be cost prohibitive. Google's stuff is a mix of lidar, satellite, standard aerial photos, etc. From what I can see, it's not Orthophoto quality. It's for reference. Rubber sheeting can help, but there will still be error. You can probably get it as tight as you used to get with a Salztman vertical rectifying projector, but not much better than that. Cool tool for diplays and tax maps, but I would not take it any further.