Enhanced Camera Trigger Geotagging

First of all, Mission Planner rocks!! As it has since I started using it years ago!!

I'm in the process of testing out the enhanced camera trigger with RTK GPS. To check the viability of not using Ground Control. I have a highly accurate test location setup with around 20 control points set with mm accurate survey equipment.
I am using the standard 3DR GPS for Navigation and a Piksi as GPS2 for logging and processing after the flight (mainly because the Piksi RTK is too flaky for flight navigation). I'm currently flying with a Sony A7 using the Tuff Wing Hot Shoe cable. Everything works great!!
My only issue is how do I geotag the images with the precise lat, long, alt position of GPS2 and the roll, pitch, yaw?
The CAM messages that are created correspond to GPS1 and the sampling rate of my GPS2 isn't fast enough to log at the speed I'm flying (~7m/s), unless I interpolate manually. Can I get the CAM message to use GPS2 instead of GPS1? Or is there a better way to do what I'm trying? Also, can the geotag utility in Mission Planner interpolate based on the before/after GPS2 positions and use the GPS2 speed to get a more accurate geotag position?
This may not seem necessary, but when using such an accurate GPS it is definitely needed.
I have a Reach GPS on the way as well so I can test the two against each other. I know they have a Hot Shoe setup that will tag the RINEX file when the camera fires as well. I'm planning to use that for post-processing. I will post my results once everything is complete and processed.

Thanks!
Steve

Start with Mission Planner’s geotag utility and CAM-message handling, then trace how GPS1 and GPS2 positions, rates, and attitude data are selected. Done would require a defined, verified approach for GPS2-based geotagging in the enhanced camera-trigger workflow, including interpolation if supported.

Written by the indexing model from the issue text.