I added reinforcements to the center brackets by welding a 90 degree brace to each outside bracket. It worked very well to keep the top of the bunks from leaning. While the brackets were still hot from welding, I sprayed them with a couple of coats of cold galvanizing paint and they aren't rusting from 2 years of saltwater baths.
Not sure how to "double up" though, none of the holes line up if you just add another factory bracket.
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2004 Trophy 2902 WA with Merc 225 EFIs
Sucks gas and hauls ass!

One step ahead and you are a genius, two steps ahead and you are a misfit.