It looks great, I could have a need for one in aquatic weed control. Having the props protected in swamps from old trees, reeds, dead sticks etc would be a bonus. It seems you've gone for looks and prop protection rather than efficiency. I know from my days with hovercraft you can get more thrust with a properly designed ducted fan than you can with open props. You have to slow the air speed down after the props. This is done by tapering the duct in slightly after the props thus increasing the air pressure on the underside. Slats on the rear of the duct, tapered in the opposite direction to the air swirl also help too. This seems counter intuitive but it works, slowing down the air flow and and keeping the thrust forces perpendicular to the props. The design of the front of the duct is important too. Correctly done, it produces  a low pressure dome above the props. The air intakes on ducted fan jets are not there for looks. Hopefully all the above will not create too much weight. There is a whole science dedicated to ducted fans.