It does look good...! But I also wonder how it will hold up over time. Assuming the sink is 10" deep, using your other measurements, it's approx. 1.9 cubic feet. Full to the brim with water, the water will weigh approx. 118 lbs. Of course, you'll seldom have it anywhere near full, but that's a lot of potential weight for a fairly thin bottom, approx 2.3 square feet. Hopefully, the layers of fiberglass wrapped around the bottom edges and on the bottom will provide sufficient strength.
(Note: In the volume calcs, I did not deduct the corner areas behind the curves.)
