Using multiple flight logs for geolocation

Sometimes, instead of processing multiple missions as separate projects, then merging, I would like to process them as a single project. 

I geolocate the images with a 3DR flight log, using the CAM trigger function. 

Is there a way I can get P4D to accept multiple log files?

That failing, is there a way I can merge the flight logs, so that I can P4D to match the images to the right CAM trigger?

How does P4D match the CAM to the image? Is it just sorted by time (i.e. the first CAM is attributed to the image with the earliest time stamp)?

I have tried to use the import 3DR log but it never matches the locations correctly. I always have one or two images that get no locations and the lat and longs imported do not match the log from my pixhawk even though the number of cam messages match the number of images captured… Shame because Pix4D calculates omega phi kappa from the roll pitch and yaw. I have been exporting all my flight logs as .csv and then creating one master log.