Unfortunately I cannot help you with the specifics of building a bracket due to the fact that I am in the business of building and selling fiberglass outboard brackets. There are several guys on this forum who have built their own that you can check out. I do think that if you are going to go thru the effort of designing,making a mold, and building your own you would be well served to use poly cores instead of plywood. The extra cost will be well worth it down the line.
