First, slider gallery:
Have been experimenting with this for my own sites and I have a feeling that the solution is simply that the images aren't the right size. Need 1200x500 and that's rarely the size. Simple solution is to stitch two pics 600x500 together and upload as one. Will test my theory...
I took a look at the images in the current folder and they are a mix of high and low res. which affects loading time.
I think one approach is for someone with bandwidth to download the whole folder, take the sailing images, resize, stitch into pairs, upload into slider gallery (supposing my theory is correct)
Future inclusion into slider based on images conforming to size and resolution. High res no good for quick loading and online viewing.
Google no substitute for our members pics IMHO!
You said the following which I totally agree with!
We could reduce the size of the Photo Gallery by simply deleting all images that don't have a caption, and adding a warning that that will happen in the future.