Thanks for the test build dfort!
I gave it a quick test, taking a couple of rough and ready shots just in my front room. As far as i could tell, i don't think it made any difference though. I'd need to do a more thorough test to be absolutely sure though.
However, this got me thinking, for what i'm trying to achieve here, i suppose it doesn't really matter if the Raw video doesn't exactly match the H.264 one. For me, what matters the most, is that what is displayed on the camera screen itself is exactly what is captured in the Raw video. With this in mind, i tried changing the 'Preview Options' under the Raw Video (MLV) section from Auto to 'ML Grayscale'. There is a note at the bottom of the screen that says 'Looks ugly, but at least framing is correct'. And indeed, when choosing this option i can see the framing suddenly shift in the required direction! It's true that it does indeed look ugly (the resolution is terrible, everything looks blocky as hell) but i took a quick video (lining up something in the very corner of the frame) and the resulting DNG files seemed to put it right in the corner, so i think i may have stumbled into a solution here by accident! I think i can live with the ugly preview issue, i'm hoping i will still be able to make out the features of the moon well enough to know where i am in terms of putting together the mosaic.
One thing i've noticed though, this means i have to have Global Draw on in Liveview (to take advantage of the ML Grayscale option). Global Draw adds a row of information at the top and bottom of the screen. Normally this information is desirable, but in my case it's simply getting in the way of important screen real estate, as what is underneath is still being captured. As a workaround, I can tap the Q button to get a peak through Canon's semi-transparent bar to see what's under there, but it would obviously be preferable to not have to touch the camera at all. I don't think it's possible, but it would be nice to have the option to turn these info strips off but keep Global Draw on in Liveview. Just a thought i suppose!
As for everything else above that's gone before, if you guys still think the issue with the offsets needs updating then i'm happy to continue to help with taking test shots and testing out any new builds.
Thanks everyone for all your help on this, you're all lovely people.
Cheers,
xiga.