This is the same basic design as https://www.thingiverse.com/thing:4975973, but the top shape is formed from an ellipse so it has rounded ends. The bottom is not flat either; I used a scaled sphere to subtract most of the material in the bottom in an effort to reduce the amount of infill that gets printed.

I printed this piece with no supports, so the inside surface of the bottom didn't come out very well. But the top side of the print is just fine. Depending on how your printer works you may want to print this one with supports for the bottom center.

FLSun SuperRacer

No

No

200

7% Rectilinear