Structual engineer and 3d design for boat trailer

I need help with the structural engineering calculations and design for 3-5 boat trailers that will be used to tow boat over 20 feet in length. 20-22 22-24 24-26 26-28 28-30 30-32 32-34 34-36 etc The trailer must be designed as a tri-axle trailer and a dual axle trailer for less weight. some existing drawings/pictures and dimensions are available to work from. I need an experienced professional to come up with a durable design that will meet the requirements of this project. A USA licensed engineering stamp will be required. Engineering stamp can be anywhere in USA. The freelancer could also provided the final plans for the stamp to be approved by a local engineer. Intellectual rights and property, also need all original cad drawings and lists of parts and dimensions and specs. This is to be made of aluminum and a galvanized steel option as well for cost savings. Stainless hardware for the aluminum series and galvanized for the other. Renderings and 3d files for our website will also be required. At least 4 revisions after initial set is complete to make sure it is 100% and certified.