This solution requires drilling 4 holes in the shell:
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This is a special flat base bracket that mates well to the relatively flat sides of the Dolphin shell.
I was worried about cracking the shell so I used nylon fender washers (larger outside diameter than standard washers) to spread the load where the bolts go through to screw into the bracket. I also used a flattish round headed phillips screw on the inside so that there would be no sharp edges against the counter lungs.