Jimp...the images actually look really good to me....
I don't own Lowrance...so I don't know a lot about their settings.....
About the only things that would be interesting to experiment with would be to tic the Sensitivity down just a little to maybe remove some of the "brighter washouts" in parts of the image..(this even sometimes makes the shadows from structure more distinguishable)...
Another interesting experiment to try when you find a piece of structure like this...is to set the SI to 1 side only.....(This will Zoom that side's image..without having to "Freeze" the image and use the "Zoom cursor")....
Still...great shots jimp....good job.....
Rickie