Try using your GoPros in 'Wide'.
You'll get a lot more coverage.
My 7s go a bit soft on the sides of the images, but sharp in the middle. The wider field of view still
I've scanned A LOT of reef, including several hundred meters of a sloping reef (3m reef flat to 35m) and only got a 'little' bit of banana.
I've read that doing some extra passes with the cameras angled slightly up from nadir helps fix this, and also with a slightly different heading, 15 degrees off say. Would love to get some technical explanation of this. I've read it where people do this for drone scans.
My setup:
3x GoPro 7 on a 4m pipe, so a 2m pitch.
2s Timelapse Photos
Altitude 3m in shallows, 4m normal to the reef in the area of interest (5-20m). 5-6m when deeper (didn't need as much detail).
Swimming at sustained cruising speed for the whole dives, gives a bit extra forward overlap... Shame GoPros don't have a 3s interval.
Trick for poll flapping. Add helical strakes in the form of thin rope, spirally wound around the pipe (water pipe in my case). Jubilee Clipped to hold it. This mimics what industrial chimneys use, to prevent oscillation and destruction by the wind! My setup has about 1 turn per foot... But i'll probably change to thicker rope or have 2 ropes spiralling, as i still get a bit of oscillation. Google "helical strakes" and you'll know what i'm on about. But with shorter pipes, probably not needed for your case. The bigger pitch, higher flying are great for mapping huge areas, giving context to highly detailed scans.
And i'm doing 2x whole AL80 per 1hr dive!
Here's my long scan:
https://skfb.ly/orW9XI haven't gotten around to measuring the distances or depths properly yet. But you'll see its a looooooong transect by looking at the bommies/coral heads!