Heavy Duty Hole Cover or End Cap for 3.5 Inch Hole (Scalable)

A friend has a house boat which has 3.5 inch diameter receiving holes/sockets on the deck where a winch is inserted. When the winch is not in use, the holes are exposed, leaving a chance that something might fall into the sockets (keys, watch, phone, etc.). He could not find pre-made 3.5" hole covers. I designed these two cap options: one with a solid top, and one with two finger holes (to aid in removing the cap). I made the cap quite sturdy, so that it can be walked on. As is, the models are specifically for a 3.5" hole, but they can be easily scaled to fit different size requirements.

The stock model is 4" in diameter (there is a 0.25" lip), by 2" in total height (the top is 0.25" thick, making the cap insert into the hole 1.75").

My friend said that gray would be a good color, so I printed in this CC3D Marble PLA, at 0.20mm layer height, 100% infill (for sturdiness), with a 0.4mm nozzle. One cap uses about 125 grams of filament at these settings. The model prints upside down (the download orientation). I printed with a textured PEI plate and the top surface of the caps turned out excellent.

Note: the houseboat is 300 miles (643 km) away, so he won't be able to see how the design fits until he goes on vacation in a month. So, I had to make my best estimate on the fit; it has yet to be tried out. :D